Diagnostic library
1,272 OBD-II Trouble Code GuidesA code is the first clue.
Use the AutoLogicTools library to understand what a scan-tool result means. A code is a starting point for diagnosis, not proof that a particular part has failed.
Search or browse 1,272 detailed OBD-II trouble code guides. Entries include, where applicable, plain-English definitions, symptoms, common causes, diagnostic steps, severity, repair options, repair-cost ranges, DIY difficulty, and related trouble codes.
Powertrain (P codes)
Engine, transmission, fuel, ignition, and emissions codes. 858 codes published.
Fuel Volume Regulator Control Circuit/Open
The PCM has detected an open in the control circuit for the fuel volume regulator — the valve that meters how much fuel the high-pressure pump delivers to the rail. On direct-injection and diesel engines this regulator sets fuel rail pressure, so an open control circuit can mean the PCM can't regulate pressure properly. The usual causes are wiring, the connector, or the regulator (suction control valve) itself.
Read this codeFuel Volume Regulator Control Circuit Range/Performance
The fuel volume regulator is being commanded normally and is answering electrically, but the fuel pressure that results is not what the command should have produced. This is the one code in the P0001-P0004 group that can set with a perfectly healthy circuit, which makes the fuel supply feeding the pump the first thing to look at rather than the last.
Read this codeFuel Volume Regulator Control Circuit Low
The control wire for the fuel volume regulator is sitting at a lower voltage than the module intended, normally because it has found a path to ground. Whether that leaves you with a car that will not start or a car that over-pressures the fuel rail depends entirely on which way the valve fails, and that answer is different between manufacturers.
Read this codeFuel Volume Regulator Control Circuit High
The module sees more voltage on the fuel volume regulator's control wire than it should. On a low-side driven solenoid that reading has two very different explanations — an open circuit, or a short to battery voltage — and telling them apart takes one measurement that most people skip.
Read this codeFuel Shutoff Valve "A" Control Circuit/Open
The module found no electrical load on the fuel shutoff valve's control leg. Before diagnosing anything, establish whether this valve has to be energised to run or energised to stop — the answer inverts the symptom completely.
Read this codeFuel Shutoff Valve "A" Control Circuit Low
Voltage on the shutoff valve's control leg is being pulled down when it should not be. On an energise-to-run design that leaves the valve permanently open — the engine runs, and the key can no longer stop it.
Read this codeFuel Shutoff Valve "A" Control Circuit High
The shutoff valve's control leg is sitting higher than commanded. On an energise-to-run design the valve springs shut, and this becomes the member of the block that leaves you calling a tow truck rather than driving in.
Read this codeEngine Position System Performance Bank 1
This is a geometry code, not an electrical one. The module is reporting that the angle between the camshafts and the crankshaft on bank 1 has drifted out of tolerance — and the free thing to check first is the oil.
Read this codeEngine Position System Performance Bank 2
A bank 2 code proves the engine has two cylinder heads, which means duplicated timing hardware. Whether this code arrived alone or with its bank 1 twin is the single most informative thing about it.
Read this code'A' Camshaft Position Actuator Circuit (Bank 1)
The intake camshaft position actuator on bank 1 has an electrical fault — the PCM is either not seeing the response it expects from the VVT solenoid, or the circuit itself is open or shorted. Almost always an oil-related issue at the root.
Read this codeCamshaft Position A — Timing Over-Advanced or System Performance (Bank 1)
The intake camshaft on Bank 1 is more advanced than the engine computer commanded. Most often caused by a stuck variable valve timing (VVT) solenoid or dirty engine oil. Address promptly — neglected timing issues can damage the engine.
Read this codeCamshaft Position A — Timing Over-Retarded (Bank 1)
The intake camshaft on Bank 1 is more retarded (lagging) than the engine computer commanded — the opposite of P0011. Most often a stuck VVT solenoid or dirty engine oil preventing the cam from advancing on command.
Read this code'B' Camshaft Position Actuator Circuit (Bank 1)
The exhaust camshaft position actuator on bank 1 has an electrical fault. The PCM is sending a command to the exhaust VVT solenoid and not seeing the electrical response it expects — usually because of oil contamination, a failed solenoid, or wiring damage.
Read this codeCamshaft Position B — Timing Over-Advanced or System Performance (Bank 1)
The exhaust camshaft on Bank 1 is more advanced than the engine computer commanded. Most often caused by a stuck VVT solenoid on the exhaust cam, dirty engine oil, or a stretched timing chain on high-mileage engines.
Read this codeCamshaft Position B — Timing Over-Retarded (Bank 1)
The exhaust camshaft on Bank 1 is more retarded than the engine computer commanded. The 'B' camshaft is the exhaust cam on dual-VVT engines. As with all over-retarded cam codes, dirty oil or a stuck VVT solenoid lead the suspect list.
Read this codeCrankshaft Position — Camshaft Position Correlation (Bank 1, Sensor A)
The relationship between the crankshaft and intake camshaft on Bank 1 is outside the expected window. Often a stretched timing chain — known issue on Hyundai/Kia 2.4L Theta II, BMW N20/N26, Audi 2.0T, and other timing-chain engines. Don't ignore it.
Read this codeCrankshaft Position — Camshaft Position Correlation (Bank 1, Sensor B)
The relationship between the crankshaft and exhaust camshaft on Bank 1 is outside the expected window. Same root causes as P0016 — often a stretched timing chain. Don't ignore it.
Read this codeCrankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A)
The PCM compared the crankshaft position to the bank-2 intake camshaft position and found them out of sync beyond what variable valve timing should produce. Usually means the timing chain on bank 2 has stretched, the phaser is mechanically off, or the cam sensor is reading incorrectly.
Read this codeCrankshaft Position - Camshaft Position Correlation (Bank 2 Sensor B)
The PCM compared the crankshaft position to the bank-2 exhaust camshaft position and found them out of sync beyond the VVT operating range. Almost always a mechanical timing problem — chain stretch, worn phaser, or a failing exhaust cam sensor on bank 2.
Read this code'A' Camshaft Position Actuator Circuit (Bank 2)
The PCM is commanding the intake-camshaft VVT solenoid on bank 2, but the electrical feedback it's getting back doesn't match what it expects — usually an open, short, or wiring fault in the solenoid circuit on the bank-2 side of the engine.
Read this code'A' Camshaft Position Timing Over-Advanced or System Performance (Bank 2)
The intake camshaft on bank 2 isn't holding the timing position the PCM commanded — it's reading further advanced than expected. The electrical side of the VVT solenoid is fine; the camshaft itself isn't responding the way it should.
Read this code'A' Camshaft Position - Timing Over-Retarded (Bank 2)
The intake ('A') camshaft on Bank 2 is timed too far retarded compared to what the computer commanded. The check engine light is on and the engine may run rough or feel down on power.
Read this code'B' Camshaft Position Actuator Circuit (Bank 2)
The PCM detected an electrical fault in the exhaust-camshaft VVT solenoid circuit on bank 2. 'B' designates the exhaust cam — the one that controls when the exhaust valves open relative to crankshaft position.
Read this code'B' Camshaft Position Timing Over-Advanced or System Performance (Bank 2)
The exhaust camshaft on bank 2 is sitting further advanced than the PCM commanded — the solenoid is responding electrically, but the cam itself isn't tracking the commanded position. Usually oil, phaser, or chain related.
Read this code"B" Camshaft Position Timing Over-Retarded (Bank 2)
The exhaust ("B") camshaft on bank 2 is staying more retarded than the engine computer commanded. Usually an oil-flow or VVT solenoid problem rather than a broken part.
Read this codeIntake Valve Control Solenoid Circuit Range/Performance (Bank 1)
The variable valve timing solenoid for the intake camshaft on Bank 1 isn't controlling cam position within its expected range. The check engine light is on and the engine may run rough or feel down on power.
Read this codeExhaust Valve Control Solenoid Circuit Range/Performance (Bank 1)
The exhaust camshaft phaser on Bank 1 is not moving the way it was commanded to. On a large share of modern engines the exhaust cam is what does the job an EGR valve used to do, so this code usually shows up as a rough cold idle and an emissions failure rather than as lost power.
Read this codeIntake Valve Control Solenoid Circuit Range/Performance (Bank 2)
The intake camshaft phaser on Bank 2 is not tracking its commanded position. Because intake cam timing sets how much air the cylinders actually take in, this code very often announces itself as a one-bank fuel trim problem — and the lean code for Bank 2 frequently arrives before this one does.
Read this codeExhaust Valve Control Solenoid Circuit Range/Performance (Bank 2)
The exhaust camshaft phaser on Bank 2 is not achieving its commanded position. What sets this code apart from the rest of the variable valve timing family is a cost question: on most V engines each bank has its own secondary chain and tensioner, and reaching this phaser opens the timing cover — so the quote is usually about the chain, not the solenoid.
Read this codeHO2S Heater Control Circuit (Bank 1, Sensor 1)
The module found a fault in the heater control for the upstream oxygen sensor but did not classify it as high or low. That missing direction is the whole character of this code — every other heater code hands you a starting point, and this one makes you establish it yourself from current data.
Read this codeHO2S Heater Control Circuit Low (Bank 1, Sensor 1)
The heater circuit in the upstream oxygen sensor is drawing less than it should. Bank 1 is the one bank every engine has — including every four-cylinder — which means on most vehicles setting this code there is no second sensor to compare against, and the diagnosis has to be absolute rather than comparative.
Read this codeHO2S Heater Control Circuit High (Bank 1, Sensor 1)
The engine computer detected too much voltage on the heater control circuit for the Bank 1 upstream oxygen sensor — usually a short to power or a failed sensor heater. The car still runs, but warm-up fuel control and cold-start emissions suffer.
Read this codeTurbocharger/Supercharger Bypass Valve Control Circuit
The module found a fault in the circuit that operates the boost bypass valve. What the code costs you depends entirely on which kind of forced induction the car has — on a turbo it is a surge-protection device, on a supercharger it is a fuel-economy device, and the same code number means two different repairs.
Read this codeTurbocharger/Supercharger Bypass Valve Control Circuit Low
Voltage on the bypass valve control circuit sat lower than the module expected. The reason this code matters out of proportion to its cost is that the failure it usually causes — boost that builds and then leaks away — is the classic false diagnosis of a failed turbocharger.
Read this codeTurbocharger/Supercharger Bypass Valve Control Circuit High
The bypass valve control circuit read higher than the module expected. Power is usually unaffected, which is exactly why this code gets ignored — the case for fixing it is not driveability but the turbocharger's thrust bearing, which is being loaded backwards every time you lift off.
Read this codeHO2S Heater Control Circuit (Bank 1, Sensor 2)
A general heater circuit fault on the post-catalyst oxygen sensor. This sensor lives under the floor rather than on the manifold, which changes what usually kills it — and because it is the sensor the catalyst monitor depends on, this code has a habit of arriving alongside a converter code it may have caused.
Read this codeHO2S Heater Control Circuit Low (Bank 1, Sensor 2)
Too little current flowed through the post-catalyst oxygen sensor heater on the bank containing cylinder 1. The engine drives normally, but the catalyst monitor cannot finish and the vehicle will not pass an inspection.
Read this codeHO2S Heater Control Circuit High (Bank 1, Sensor 2)
The engine computer detected too much voltage on the heater control circuit for the Bank 1 downstream oxygen sensor — usually a short to power or a failed heater. The car runs normally, but the catalyst monitor won't run and it will fail an emissions test.
Read this codeTurbocharger/Supercharger Bypass Valve Control Circuit Range/Performance
The bypass valve was commanded, the circuit answered correctly, and the pressure the module expected to see never appeared. This is the one member of the family that can pass every electrical test — because the fault is usually mechanical, and most often a torn rubber diaphragm.
Read this codeO2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1
The module concluded that the two upstream oxygen sensors are reporting each other's exhaust. Almost uniquely among diagnostic codes, this one usually names a mistake rather than a failure — and because these are the sensors that control fuelling, each bank is now being corrected from the wrong evidence.
Read this codeO2 Sensor Signals Swapped Bank 1 Sensor 2 / Bank 2 Sensor 2
The two post-catalyst sensors appear to be reporting each other's exhaust. Nothing changes in how the car drives — but the catalyst monitors are now scoring the wrong converters, which is how a healthy converter on one bank gets condemned for a failing one on the other.
Read this codeHO2S Heater Control Circuit (Bank 1, Sensor 3)
A heater circuit fault on the third oxygen sensor in Bank 1's exhaust path. Only a minority of vehicles have a third sensor at all, and that rarity is itself the diagnosis — the first job on this code is to go and count sensors before anyone orders a part.
Read this codeHO2S Heater Control Circuit Low (Bank 1, Sensor 3)
The module commanded the third Bank 1 oxygen sensor's heater on and measured too little current. On this one sensor the usual labour logic is inverted — it is the easiest oxygen sensor on the car to reach, and the hardest one to get out of its bung.
Read this codeHO2S Heater Control Circuit High (Bank 1, Sensor 3)
The module saw voltage on the sensor 3 heater control circuit that it should have been holding down. Because this circuit runs the length of the underbody, the list of things it can be shorted to is nothing like the list available to an engine-bay sensor.
Read this codeTurbocharger/Supercharger Boost Control Solenoid Circuit/Open
An open or general fault in the circuit that drives the boost control solenoid — the valve that decides how much boost the engine makes at all. What you feel depends on which way the solenoid fails safe, and that is not standardised, so the symptom does not identify the fault.
Read this codeTurbocharger/Supercharger Boost Control Solenoid Circuit Range/Performance
The boost control circuit passed its electrical checks but the boost the engine actually made did not match what was asked for. This code is a verdict on the whole control loop, and the solenoid is often the innocent party in it.
Read this codeTurbocharger/Supercharger Boost Control Solenoid Circuit Low
A low reading on the boost control solenoid circuit. The catch is that this circuit is not switched on and off — it is pulsed, so an ordinary voltmeter reports an average that means nothing, and the wrong tool has condemned a lot of healthy solenoids.
Read this codeTurbocharger/Supercharger Boost Control Solenoid Circuit High
The module saw the boost control circuit sitting higher than it should. On this particular solenoid the cause is disproportionately oil — the connector lives where leaks land, and oil wicks along the strands inside the insulation until it reaches the terminals.
Read this codeTurbocharger/Supercharger Turbine Overspeed
The module has concluded that the turbo's shaft went faster than its rated limit. Almost every other code in this range reports a circuit or a plausibility failure — this one reports a mechanical limit being exceeded, and the failure mode at the far end of it is a wheel coming apart.
Read this codeHO2S Heater Control Circuit (Bank 2, Sensor 1)
A heater circuit fault on the upstream oxygen sensor of Bank 2. The part is ordinary and the access frequently is not — on a transverse V6 this is usually the sensor jammed against the bulkhead, and the labour is most of the quote.
Read this codeHO2S Heater Control Circuit Low (Bank 2, Sensor 1)
The engine computer commanded the heater in the Bank 2 upstream oxygen sensor to turn on, but measured too little voltage or current on the control circuit. Usually a failed sensor heater or a wiring fault. The car still runs, but cold-start emissions and warm-up fuel control suffer.
Read this codeHO2S Heater Control Circuit High (Bank 2, Sensor 1)
The heater in the pre-catalyst sensor on bank 2 is not drawing what the module expects. On most vehicles built this century that sensor is a wideband air/fuel device with a temperature-regulated heater, which changes what a high reading means.
Read this codeHO2S Heater Resistance (Bank 1, Sensor 1)
The module measured the upstream Bank 1 oxygen sensor heater and found its resistance outside the calibrated window. This is not a broken-circuit code — it is a specification code, and it is the reason a brand-new universal sensor can set it the day it is fitted.
Read this codeHO2S Heater Resistance (Bank 1, Sensor 2)
A resistance fault in the heater of the post-catalyst sensor on Bank 1. It changes nothing about how the engine runs — what it does is stop the catalyst monitor completing, which is how it ends up costing people a converter they never needed.
Read this codeHO2S Heater Resistance (Bank 1, Sensor 3)
A heater resistance fault on the third, rearmost oxygen sensor of Bank 1 — the coldest sensor position on the vehicle. It is the one member of this family where the season the code appeared in is real diagnostic information.
Read this codeHO2S Heater Control Circuit (Bank 2, Sensor 2)
A heater circuit fault on the post-catalyst sensor of Bank 2. Before you reach for a meter, ask what has been done to the exhaust — this is the position where two identical rear sensors get connected to each other's plugs.
Read this codeHO2S Heater Control Circuit Low (Bank 2, Sensor 2)
A post-catalyst oxygen sensor heater on the second cylinder bank drew less current than commanded. Only V-configuration and flat engines can set this code, and the sensor involved is usually the hardest one on the vehicle to reach.
Read this codeHO2S Heater Control Circuit High (Bank 2, Sensor 2)
The heater in the post-catalyst sensor on bank 2 is faulted. This sensor does not control fuelling at all — the real consequence is that the catalyst monitor never runs, so the car fails an emissions test on readiness rather than on tailpipe numbers.
Read this codeHO2S Heater Resistance (Bank 2, Sensor 1)
A heater resistance fault on the upstream Bank 2 sensor. This is the one code in the family you can diagnose by comparison — the vehicle has an identical sensor doing an identical job on the other bank, and what that one reads is the most useful number you will get.
Read this codeHO2S Heater Resistance (Bank 2, Sensor 2)
A heater resistance fault on the post-catalyst sensor of Bank 2. Resistance is a whole-loop measurement, and the ground side is part of that loop — which is why this code and its Bank 1 twin so often turn out to be one corroded splice rather than two dead sensors.
Read this codeHO2S Heater Resistance (Bank 2, Sensor 3)
The rarest position in the entire oxygen sensor heater family — the third sensor on the second bank. Its defining hazard is not electrical: parts catalogues frequently cannot say where sensor 3 physically is, so the usual failure is buying and fitting the wrong sensor.
Read this codeHO2S Heater Control Circuit (Bank 2, Sensor 3)
A heater circuit fault on the rearmost sensor of Bank 2. The module has directional codes available for this circuit and chose not to use one — which usually means the fault is intermittent, and that changes the whole approach.
Read this codeHO2S Heater Control Circuit Low (Bank 2, Sensor 3)
The heater circuit for the rearmost Bank 2 oxygen sensor is reading low. This is the longest circuit of its kind on the vehicle, which is exactly why a low reading here is so easy to misjudge.
Read this codeHO2S Heater Control Circuit High (Bank 2, Sensor 3)
The rearmost Bank 2 oxygen sensor heater circuit is sitting high. On a driven circuit like this one, high often means nothing is drawing current — and when the code arrives days after garage work, the cause is usually mechanical, not electrical.
Read this codeAir Assisted Injector Control Range/Performance
The air-assist system that atomises fuel during cold running was commanded, but the engine did not respond the way the module expected. On this code the usual culprit is carbon in the air passages, not a broken electrical part.
Read this codeAir Assisted Injector Control Circuit or Circuit Low
An electrical fault on the air-assist injector control circuit. The unusual double-barrelled title is a warning in itself: this code covers several different hardware layouts, so identify what your engine actually has before you buy anything.
Read this codeAir Assisted Injector Control Circuit High
The air-assist injector control circuit is reading high. On a solenoid circuit that usually means the module never managed to pull the line down — and a two-minute resistance check across the coil settles most of it.
Read this codeMAP/MAF - Throttle Position Correlation
The engine computer sees a mismatch between how far the throttle is open and how much air the MAP or MAF sensor reports is entering the engine. The check engine light is on and the engine may idle or accelerate poorly.
Read this codeManifold Absolute Pressure - Barometric Pressure Correlation
The manifold pressure reading and the barometric pressure reading disagree. There is one moment when they must match exactly — key on, engine off — and that free test is where this diagnosis starts.
Read this codeAmbient Air Temperature Sensor Circuit
A circuit fault on the outside air temperature sensor. It is the rare engine-side code whose main symptom is on the dashboard — and on many vehicles the signal reaches the engine module over the network, so a healthy sensor does not clear it.
Read this codeAmbient Air Temperature Sensor Range/Performance
The outside air temperature reading is electrically valid but not believable. Very often the sensor is fine and its airflow is not — which is why replacing it so frequently fails to fix this code.
Read this codeAmbient Air Temperature Sensor Circuit Low Input
Signal voltage on the outside air temperature circuit has fallen below its valid floor. Because the sensor is a thermistor whose resistance drops as it warms, a low circuit reports an absurdly HOT outside temperature — the opposite of what most people expect.
Read this codeAmbient Air Temperature Sensor Circuit High Input
Signal voltage on the outside air temperature circuit has risen above its valid ceiling, which the module converts into an impossibly cold reading. Cold is the direction with consequences — on many vehicles it shuts the air conditioning off entirely.
Read this codeAmbient Air Temperature Sensor Circuit Intermittent
The outside air temperature signal is dropping out or spiking briefly and then recovering. No static measurement will find this — the fault has to be captured on a datalog while the vehicle is moving.
Read this codeIntake Valve Control Solenoid Circuit (Bank 1)
The module found an electrical fault on the bank 1 intake valve control solenoid without classifying it as high or low. Before spending anything, establish which hardware your manufacturer means by this code — the generic list carries two parallel code sets for intake valve control.
Read this codeIntake Valve Control Solenoid Circuit Low (Bank 1)
Voltage on the bank 1 intake valve control solenoid circuit is being held below where the module expects it. A shorted coil and a shorted wire look identical from the module's side — and one connector unplug tells them apart.
Read this codeIntake Valve Control Solenoid Circuit High (Bank 1)
The bank 1 intake valve control solenoid circuit is reading higher than commanded, which on this type of output nearly always means an open. The connector sits in an oil-wetted zone, and oil wicking into it is a leading and frequently missed cause.
Read this codeExhaust Valve Control Solenoid Circuit (Bank 1)
An electrical fault on the bank 1 exhaust valve control solenoid, direction unclassified. The exhaust side of the cylinder head is a far harsher place to mount a solenoid than the intake side, and that changes which failures to expect first.
Read this codeExhaust Valve Control Solenoid Circuit Low (Bank 1)
Voltage on the bank 1 exhaust valve control solenoid circuit is being held low. Whether this code arrives alone or alongside its bank 2 twin is the most informative thing about it — two solenoids on opposite cylinder heads do not fail on the same day.
Read this codeExhaust Valve Control Solenoid Circuit High (Bank 1)
The bank 1 exhaust valve control solenoid circuit is reading high, which means current is not flowing. The break can sit on either side of the coil, and the supply side is the half most people never check because the code says nothing about it.
Read this codeIntake Valve Control Solenoid Circuit (Bank 2)
A general circuit fault on the intake valve control solenoid for bank 2. Before anything is unbolted, establish which physical cylinder head bank 2 actually is on this engine — that answer is assigned by the manufacturer, and getting it wrong is the single most expensive mistake available here.
Read this codeIntake Valve Control Solenoid Circuit Low (Bank 2)
The bank 2 intake valve control solenoid circuit is being pulled low. This is one of the rare faults where the car hands you a free known-good reference: an identical system on the other cylinder head that you can measure against and, if it comes to it, swap parts with.
Read this codeIntake Valve Control Solenoid Circuit High (Bank 2)
An open circuit on the bank 2 intake valve control solenoid. The question that narrows this fastest is not electrical — it is what work has been done to this engine recently, because the far bank's harness is disturbed by jobs that have nothing to do with valve timing.
Read this codeExhaust Valve Control Solenoid Circuit (Bank 2)
A general circuit fault on the bank 2 exhaust valve control solenoid — the hardest of the four valve control solenoid positions to reach on most V engines. That access cost inverts the usual economics: here it is worth testing properly before replacing anything.
Read this codeExhaust Valve Control Solenoid Circuit Low (Bank 2)
The bank 2 exhaust valve control solenoid circuit is shorted to ground. On this run of harness the cause is more often something mechanical pressing on the loom than the gradual abrasion people expect — worn engine mounts and rodent damage both belong on the suspect list.
Read this codeExhaust Valve Control Solenoid Circuit High (Bank 2)
An open circuit on the bank 2 exhaust valve control solenoid — the longest branch in the valve control group. A continuity check will pass on a conductor with three strands left; a voltage drop test under load will not, and that difference decides this diagnosis.
Read this codeFuel Rail/System Pressure Too Low
The fuel pressure at the rail is sitting below what the PCM is commanding under load. On direct-injection engines, this almost always points at the high-pressure fuel pump (HPFP) — not a sensor and usually not the low-pressure pump in the tank.
Read this codeFuel Rail/System Pressure Too High
The opposite of P0087. Rail pressure is sitting above what the PCM is commanding, which usually means the system can't bleed pressure off — most often a stuck or stuck-closed fuel pressure regulator on a direct-injection engine.
Read this codeFuel Pressure Regulator 1 Performance
The fuel pressure regulator isn't doing what it's been told to do — pressure isn't responding to command changes the way the PCM expects. Different from P0087/P0088 because this one flags the regulator specifically, not the rail pressure outcome.
Read this codeFuel Pressure Regulator 1 Control Circuit/Open
The control circuit for fuel pressure regulator 1 is open. On most vehicles that set this, the regulator in question is the electronic pressure control valve on the high-pressure fuel pump — not the vacuum-referenced regulator on a fuel rail that the name brings to mind.
Read this codeFuel Pressure Regulator 1 Control Circuit Low
The module is seeing a lower voltage on the fuel pressure regulator control wire than the command it issued should produce. On a pulse-width modulated circuit that is normally a short to ground, and this is the one direction where the failure can leave the regulator commanded fully on.
Read this codeFuel Pressure Regulator 1 Control Circuit High
Voltage on the fuel pressure regulator control wire is sitting higher than the command should allow. Unlike its low-side counterpart this fault often produces no drivability complaint at all — which is exactly what makes it easy to misdiagnose.
Read this codeFuel System Leak Detected - Large Leak
The module has watched fuel pressure fall faster than the system could physically lose it through normal operation, and has classified the loss as large. This is one of the few OBD codes where the right first action is to stop the engine and look for liquid fuel.
Read this codeFuel System Leak Detected - Small Leak
The module has detected a fuel pressure loss too small to explain by normal operation but below the threshold it calls large. Small leaks are harder to find than large ones precisely because they rarely produce anything you can see.
Read this codeIntake Air Temperature Sensor 2 Circuit
The module has a problem with the second intake air temperature sensor's circuit. Before anything else, find out where sensor 2 physically is on this engine — on most vehicles that set this code it is measuring charge air after the turbocharger, and it is not a spare copy of sensor 1.
Read this codeIntake Air Temperature Sensor 2 Circuit Range/Performance
The circuit is electrically fine and the reading is a believable number — it is just the wrong number. This is a plausibility fault, and the module reached it by comparing sensor 2 against the other temperature sensors on the engine rather than by measuring anything about the circuit.
Read this codeIntake Air Temperature Sensor 2 Circuit Low
Signal voltage on the intake air temperature sensor 2 circuit has fallen below its valid window. Because these sensors read backwards — low voltage means high temperature — the module is being told the charge air is impossibly hot, and its response to that is to protect the engine by taking power away.
Read this codeIntake Air Temperature Sensor 2 Circuit High
Signal voltage has risen above the valid window, which on this inverted circuit displays as the coldest reading the sensor can produce. The overwhelmingly common cause is not a short to power but an open circuit, and that makes the connector the first place to look rather than the last.
Read this codeIntake Air Temperature Sensor 2 Circuit Intermittent/Erratic
The word intermittent is the whole diagnosis. The module already caught this fault and lost it again, which means a static bench test is guaranteed to pass and the freeze frame is your test procedure.
Read this codeMass or Volume Air Flow Circuit Malfunction
The general mass airflow (MAF) circuit code — the PCM has seen a fault in the MAF sensor circuit that doesn't fit the more specific low, high, or intermittent patterns. Most often a dirty sensor, a wiring or connector problem, or unmetered air entering the intake.
Read this codeMass Air Flow Sensor Range/Performance Problem
The engine computer detected that the mass airflow (MAF) sensor reading doesn't match expected values based on throttle position and engine speed. Most often caused by a dirty MAF sensor — cleaning resolves a large share of cases.
Read this codeMass Air Flow Sensor Circuit Low Input
The engine computer detected that the mass airflow (MAF) sensor signal is reading too low — often because the sensor is disconnected, the wiring is damaged, or the sensor itself has failed. The engine may run rough or stall.
Read this codeMass or Volume Air Flow Circuit High Input
The mass airflow (MAF) sensor is reporting more airflow than the PCM thinks is physically possible. Two main causes: unmetered air sneaking into the engine after the sensor, or a contaminated sensor over-reporting.
Read this codeMass or Volume Air Flow Circuit Intermittent
The mass air flow (MAF) signal is cutting in and out. Unlike the steady MAF circuit codes, P0104 is the intermittent one — the sensor works most of the time, then briefly drops or spikes before recovering. That on-again-off-again behavior usually points at a connector or wiring problem, MAF contamination, or electrical noise rather than a flat-dead sensor, and it can make the engine hesitate or stumble unpredictably.
Read this codeManifold Absolute Pressure/Barometric Pressure Circuit Malfunction
The engine computer sees an electrical fault in the MAP (manifold absolute pressure) sensor circuit — the signal is missing, stuck, or not changing the way it should.
Read this codeManifold Absolute Pressure/Barometric Pressure Circuit Range/Performance
The MAP (or barometric pressure) sensor is reading a value that is electrically valid but implausible for current engine conditions. The ECM sees a pressure signal that doesn't match throttle position, RPM, and airflow, so it flags the sensor's performance.
Read this codeManifold Absolute Pressure/Barometric Pressure Circuit Low Input
The MAP/BARO sensor signal voltage has dropped below the normal operating range. The ECM sees a signal that's too low to be valid, usually pointing at a wiring short, a disconnected sensor, or a failed sensor.
Read this codeManifold Absolute Pressure/Barometric Pressure Circuit High Input
The MAP/BARO sensor signal voltage is above the normal operating range. The ECM is effectively being told the manifold is at or above atmospheric pressure at all times, which throws off fueling and can make the engine run rich, rough, or down on power.
Read this codeManifold Absolute Pressure/Barometric Pressure Circuit Intermittent
The MAP/BARO signal drops out, spikes, or glitches briefly rather than failing outright. The engine may stumble, surge, or hesitate at random, and the fault often disappears before you can find it — connectors and chafed wiring are the usual culprits.
Read this codeIntake Air Temperature Sensor Circuit Malfunction
The PCM has flagged a general fault in the intake air temperature (IAT) sensor circuit — the signal is present but not behaving the way a healthy thermistor should. On a surprising number of engines, the IAT element lives inside the mass airflow sensor, which is why this code so often ends up being a MAF job.
Read this codeIntake Air Temperature Sensor Circuit Range/Performance
The IAT sensor is still sending a signal that's electrically valid — it's not pinned high or low — but the value doesn't make sense for the conditions. This is the 'plausibility' code: the number is in range, but it disagrees with what the rest of the engine is reporting.
Read this codeIntake Air Temperature Sensor Circuit Low Input
The IAT sensor signal voltage has dropped below the PCM's minimum threshold — which the computer reads as impossibly hot intake air. It's the mirror image of P0113: where that code means the circuit looks open, P0112 almost always means the signal is shorted to ground.
Read this codeIntake Air Temperature Sensor Circuit High Input
The intake air temperature (IAT) sensor signal is reading higher than the PCM's normal operating range, usually pointing to an open circuit, a failed sensor, or a wiring problem.
Read this codeIntake Air Temperature Sensor Circuit Intermittent
The IAT signal is dropping out or jumping erratically rather than failing outright — present one moment, gone the next. Intermittent codes are the hardest of the IAT family to pin down because the fault often isn't happening while the car is sitting in front of you.
Read this codeEngine Coolant Temperature Sensor Circuit Malfunction
The PCM is reporting a generic circuit fault on the engine coolant temperature (ECT) sensor — the signal is unusable for fueling calculations. Because the PCM uses coolant temp to set cold-start enrichment, a bad signal can cause hard cold starts, rich running, or stalling shortly after startup.
Read this codeEngine Coolant Temperature Sensor Range/Performance
The ECT sensor is reporting a temperature value that's within its electrical range but doesn't track engine warmup correctly. The sensor isn't electrically broken — it's drifted or sluggish, telling the PCM the wrong story about what the engine is actually doing.
Read this codeEngine Coolant Temperature Sensor Circuit Low Input
The engine coolant temperature (ECT) sensor signal is reading lower than the PCM expects — usually a short to ground in the circuit or a failed sensor pretending the engine is unrealistically hot.
Read this codeEngine Coolant Temperature Sensor Circuit High Input
The ECT sensor signal is reading higher than the PCM expects — usually an open circuit, a broken sensor, or a disconnected connector that makes the engine appear permanently cold.
Read this codeEngine Coolant Temperature Sensor Circuit Intermittent
The ECT sensor signal is dropping in and out — not cleanly failed, just unreliable. The connector is flaky, the wiring is chafing, or the sensor itself is on the way out. Intermittent codes are the hardest to chase because the signal looks fine half the time.
Read this codeThrottle/Pedal Position Sensor/Switch "A" Circuit Malfunction
The engine computer has detected a fault in the circuit for throttle position sensor A — the sensor that tells it how far the throttle is open, or on drive-by-wire vehicles, how far you've pressed the pedal. Because throttle control depends on this signal, the car may hesitate, idle badly, or drop into reduced-power mode.
Read this codeThrottle/Pedal Position Sensor 'A' Circuit Range/Performance
The throttle position sensor is reporting a value that's electrically valid but doesn't line up with what the PCM expects based on pedal input, RPM, and airflow. On most electronic throttle vehicles, this is a contaminated throttle body or a tired TPS — not always the actuator motor itself.
Read this codeThrottle/Pedal Position Sensor 'A' Circuit Low Input
The throttle position sensor signal is pegged near zero volts no matter where the pedal is. This is an electrical fault — usually an open ground, broken signal wire, or shorted-internal sensor — not a contamination issue like P0121.
Read this codeThrottle/Pedal Position Sensor 'A' Circuit High Input
The throttle position sensor signal is pegged near the 5V reference voltage no matter where the pedal is. Mirror of P0122 — usually a short to reference voltage, an open ground at the sensor, or a failed-internal-shorted sensor.
Read this codeThrottle/Pedal Position Sensor 'A' Circuit Intermittent
The throttle position signal is cutting in and out — dropping or spiking for an instant and then recovering. Classic sign of a worn sensor or a loose connection.
Read this codeInsufficient Coolant Temperature for Closed Loop Fuel Control
The engine isn't reaching the coolant temperature it needs to switch into closed-loop fuel control, so the PCM keeps running on its richer warm-up program. Nine times out of ten the culprit is a thermostat stuck open or a coolant sensor reading colder than reality — both cheap to fix, but worth catching because the side effects are poor fuel economy and a heater that never gets hot.
Read this codeInsufficient Coolant Temperature for Stable Operation
The engine never got warm enough to run in its stable, efficient operating range — nearly always a thermostat stuck open, sometimes a bad coolant temp sensor.
Read this codeIntake Air Temperature Too High
The intake air temperature reading is abnormally high — either the intake air really is too hot or, more often, the IAT sensor/circuit is skewed.
Read this codeCoolant Temperature Below Thermostat Regulating Temperature
The engine isn't reaching its normal operating temperature in the expected amount of time. The most common cause is a stuck-open thermostat. The car is drivable, but fuel economy and emissions will suffer.
Read this codeBarometric Pressure Too Low
The PCM is reading a barometric (atmospheric) pressure value below the lowest figure it considers physically believable. Almost always a sensor, port, or wiring fault rather than actual weather — the plausibility window is wide enough to cover real altitude and storms.
Read this codeO2 Sensor Circuit Malfunction (Bank 1, Sensor 1)
The upstream oxygen sensor on bank 1 is producing a signal the ECM considers out of range or non-responsive. This is the sensor before the catalytic converter that the ECM uses to trim the fuel mixture in real time.
Read this codeO2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 is reporting a voltage that's too low for too long. The sensor may be reading stuck-lean, the wiring may be shorted to ground, or an exhaust leak may be letting in extra air.
Read this codeO2 Sensor Circuit High Voltage (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 is reporting a voltage that's too high for too long. The sensor may be reading stuck-rich, the wiring may be shorted to power, or the engine may actually be running rich.
Read this codeO2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 is responding too slowly when the air-fuel ratio changes. Almost always caused by an aging sensor that has lost the ability to switch quickly. Replacement resolves nearly all P0133 cases.
Read this codeO2 Sensor Circuit No Activity Detected (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 isn't switching at all — the signal is flatlined. Often caused by a disconnected sensor, broken wire, or a failed heater that prevents the sensor from reaching operating temperature.
Read this codeO2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
The internal heater for the Bank 1 upstream oxygen sensor failed. The sensor still works once exhaust heat brings it up to temperature, but it takes longer — meaning slower closed-loop operation and worse cold-start emissions.
Read this codeO2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
The downstream oxygen sensor circuit on bank 1 isn't behaving the way the PCM expects — the generic bank-1, sensor-2 circuit fault (the specific low- and high-voltage versions are P0137 and P0138). Either the sensor itself is failing, the wiring is faulty, or the catalyst has changed how exhaust flows past the sensor.
Read this codeO2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
The downstream oxygen sensor on bank 1 is reporting a voltage that's stuck low — sitting near zero and refusing to rise. The usual culprits are a signal wire shorted to ground, an open circuit, an exhaust leak pulling in fresh air, or a worn-out sensor.
Read this codeO2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
The downstream oxygen sensor on bank 1 is reporting a voltage that's stuck high — pinned near the rich end of the scale and staying there. Usually the sensor signal wire has shorted to a power source, the sensor is contaminated, or the engine genuinely is running rich.
Read this codeO2 Sensor Circuit Slow Response (Bank 1, Sensor 2)
The downstream oxygen sensor on bank 1 still works, but it reacts too slowly. The PCM ran a response-time test, forced a change in exhaust mixture, and the sensor took longer than allowed to follow it — the classic signature of a 'lazy', aging sensor.
Read this codeO2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
The downstream oxygen sensor on bank 1 isn't producing a signal at all — the voltage is flat, stuck at a single value, or the PCM sees no response when it would expect one. Different failure mode from P0136 (low voltage): no signal, not a low one.
Read this codeO2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
The internal heater for the Bank 1 downstream oxygen sensor failed. The sensor monitors catalyst efficiency rather than fuel trim, so driveability is unaffected — but the code prevents emissions test compliance.
Read this codeO2 Sensor Circuit Malfunction (Bank 1, Sensor 3)
The engine controller cannot get a usable signal from the third oxygen sensor on Bank 1. Before spending a cent, confirm the vehicle actually has a third sensor on that bank — most do not.
Read this codeO2 Sensor Circuit Low Voltage (Bank 1, Sensor 3)
The third oxygen sensor on Bank 1 is reporting a persistently low voltage. The decisive question is whether that low reading is flat or still moving — one means a wiring short, the other means air is getting into the exhaust.
Read this codeO2 Sensor Circuit High Voltage (Bank 1, Sensor 3)
The Bank 1 Sensor 3 signal is reading above what the sensor is physically capable of producing. That arithmetic is the diagnosis: the extra voltage is coming from somewhere else in the harness.
Read this codeO2 Sensor Circuit Slow Response (Bank 1, Sensor 3)
The Bank 1 Sensor 3 signal is moving in the right direction but taking too long about it. At this position, check the heater before you check the sensor — the two are usually the same story.
Read this codeO2 Sensor Circuit No Activity Detected (Bank 1, Sensor 3)
The Bank 1 Sensor 3 trace has gone flat. What voltage it is flat at splits the diagnosis three ways before you pick up a single tool.
Read this codeO2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 3)
The heater inside the third Bank 1 oxygen sensor has failed. At this position the heater is not an accelerant — it is the only thing that gets the sensor working at all, which is why this code rarely arrives alone.
Read this codeFuel Delivery Error
The module is reporting that actual fuel pressure does not match what it asked for. It does not know why, and it does not know which side of that comparison is lying — which is why the return-flow test matters more than the pump.
Read this codeFuel Timing Error
Delivery is how much fuel; timing is when. Which repair path this code puts you on depends entirely on whether the engine has a mechanical injection advance mechanism or none at all.
Read this codeO2 Sensor Circuit Malfunction (Bank 2, Sensor 1)
The upstream oxygen sensor on Bank 2 is not giving the controller a usable signal. This is the one oxygen sensor code that genuinely changes how the engine runs — half the engine loses its fuel feedback.
Read this codeO2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
The upstream oxygen sensor on bank 2 is reporting a voltage stuck near zero — meaning either the sensor sees a constantly lean mixture, the sensor itself has failed, or there's a wiring break between the sensor and the PCM.
Read this codeO2 Sensor Circuit High Voltage (Bank 2, Sensor 1)
The bank 2 upstream oxygen sensor is reporting voltage stuck high — usually around or above 0.9V — which means the sensor is seeing a rich exhaust mixture, has been contaminated, or has been short-circuited to a voltage source. Different problem set from P0151, even though they sit on the same connector.
Read this codeO2 Sensor Circuit Slow Response (Bank 2, Sensor 1)
The upstream oxygen sensor on bank 2 is switching too slowly. It still works, but it has gotten lazy — it no longer flips between rich and lean fast enough for the PCM to trim fuel accurately. This is the bank-2 mirror of P0133, and on a high-mileage engine an aged sensor is the usual answer, though an exhaust leak or contamination near the sensor can mimic it.
Read this codeO2 Sensor Circuit No Activity Detected (Bank 2, Sensor 1)
The upstream oxygen sensor on bank 2 has gone flat — the PCM sees no switching activity at all, just a stuck or dead signal. Unlike slow response (P0153), this is the bank-2 mirror of P0134 and means the sensor has effectively stopped reporting, often from a failed sensor, a dead heater, an open circuit, or a wiring problem. The engine falls back to open-loop fuel control, so expect worse economy.
Read this codeO2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)
The internal heater in the upstream oxygen sensor on bank 2 isn't drawing the current the PCM expects. Either the heater element has failed, the supply or ground wire is broken, or the PCM driver isn't switching the circuit on.
Read this codeO2 Sensor Circuit Malfunction (Bank 2, Sensor 2)
The downstream oxygen sensor circuit on bank 2 isn't behaving the way the PCM expects — the generic bank-2, sensor-2 circuit fault (the specific low- and high-voltage versions are P0157 and P0158). Same fault pattern as P0136, but on the cylinder bank that does not contain cylinder 1 — and the labor estimate often runs higher because of access.
Read this codeO2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)
The downstream oxygen sensor on bank 2 is reading persistently low — a steady lean-looking voltage that won't come up. As the bank-2 mirror of P0137, the usual suspects are an exhaust leak near the sensor letting in outside air, a genuine lean condition, or a failed sensor or wiring fault. Because this is a post-catalyst sensor, the driveability impact is usually small, but it can muddy catalyst monitoring.
Read this codeO2 Sensor Circuit High Voltage (Bank 2, Sensor 2)
The downstream oxygen sensor on bank 2 is reading persistently high — a steady rich-looking voltage that won't drop. As the bank-2 mirror of P0138, the usual causes are a genuinely rich condition, a sensor or wiring fault (a short to voltage or a contaminated sensor), or coolant/fuel contamination. Because it's a post-catalyst sensor, driveability is often unaffected, but a real rich condition behind it can foul plugs and overheat the converter.
Read this codeO2 Sensor Circuit Slow Response (Bank 2, Sensor 2)
The downstream oxygen sensor on bank 2 is responding too slowly. It's the bank-2 mirror of P0139 and the lowest-stakes of the bank-2 O2 codes: a rear sensor that has gotten lazy. An aged sensor is the usual cause, and because this sensor mainly watches catalyst efficiency rather than trimming fuel, the practical impact is small — mostly a check engine light and a failed emissions test.
Read this codeO2 Sensor Circuit No Activity Detected (Bank 2, Sensor 2)
The downstream oxygen sensor on bank 2 isn't producing any signal — the voltage is flat or stuck at a single value. Same failure mode as P0140, but on the cylinder bank that does not contain cylinder 1, with the same bank-2 labor premium.
Read this codeO2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 2)
The heater inside the downstream oxygen sensor on bank 2 isn't drawing the current the PCM expects. The sensor itself may produce a signal, but the heater that brings it to operating temperature has failed or has a wiring issue.
Read this codeO2 Sensor Circuit Malfunction (Bank 2, Sensor 3)
The third oxygen sensor on Bank 2 is not reporting usefully. This is the rarest sensor position on any vehicle, and the hard part is buying the right part rather than working out what is wrong.
Read this codeO2 Sensor Circuit Low Voltage (Bank 2, Sensor 3)
The third oxygen sensor on Bank 2 is reporting persistently low voltage. Because an identical sensor is fitted in the same position on the other bank, this is one of the few oxygen sensor codes you can settle by direct comparison instead of by specification.
Read this codeO2 Sensor Circuit High Voltage (Bank 2, Sensor 3)
The third oxygen sensor on Bank 2 is reporting a voltage the element cannot produce on its own. On this bank the wiring has to cross the engine to reach the controller, and that long, hot routing is where the fault usually lives.
Read this codeO2 Sensor Circuit Slow Response (Bank 2, Sensor 3)
The third oxygen sensor on Bank 2 is changing its reading too slowly. On a bank whose feed and ground are the long ones, the usual reason is a heater that is not getting the current it needs — and a continuity test will not show that.
Read this codeO2 Sensor Circuit No Activity Detected (Bank 2, Sensor 3)
The third oxygen sensor on Bank 2 has gone silent. The most useful first question is not which meter to reach for — it is what was done to the vehicle recently, because this connector is the one that gets disturbed by other jobs.
Read this codeO2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 3)
The heater inside the third oxygen sensor on Bank 2 is not behaving as commanded. Because this vehicle has two of everything downstream, the question that decides the bill is whether one heater failed or something they all share did.
Read this codeFuel Temperature Too High
The engine controller believes the fuel reaching the engine is hotter than it should be. This is a condition report rather than a circuit fault, so the first job is deciding whether the fuel really is hot.
Read this codeIncorrect Fuel Composition
The controller has concluded that what is in the tank is not the fuel it expects. On this code the most informative diagnostic tool is the receipt from the last fill-up.
Read this codeFuel Trim Malfunction (Bank 1)
The PCM is reporting fuel trim on bank 1 is out of range, but unlike P0171 (lean) or P0172 (rich), this code doesn't commit to which direction. Most readers find this code after looking at P0171 or P0172 first — the diagnostic path here forces an extra step.
Read this codeSystem Too Lean (Bank 1)
The engine computer detected that Bank 1 is running with too much air or too little fuel. The check engine light is on and you may notice rough idling or hesitation, but the car is usually still drivable.
Read this codeSystem Too Rich (Bank 1)
The engine computer detected that Bank 1 is running with too much fuel or too little air. The check engine light is on; you may see black exhaust smoke, smell fuel, and notice rough idling or poor fuel economy.
Read this codeFuel Trim Malfunction (Bank 2)
The PCM has decided fuel trim on bank 2 is out of acceptable range — but unlike P0174 (lean) or P0175 (rich), this code doesn't commit to which direction. The first diagnostic question is whether the trim is being pulled lean, pushed rich, or oscillating between them.
Read this codeSystem Too Lean (Bank 2)
The engine computer detected that Bank 2 is running with too much air or too little fuel. Same condition as P0171, but on the opposite side of a V-configured engine. Only applies to V engines.
Read this codeSystem Too Rich (Bank 2)
The engine computer detected that Bank 2 is running with too much fuel or too little air. Same condition as P0172, but on the opposite side of a V-configured engine. Only applies to V engines.
Read this codeFuel Composition Sensor Circuit Malfunction
The flex-fuel composition sensor circuit has faulted. This is a flex-fuel (E85-capable) vehicle code — the sensor tells the PCM how much ethanol is in the tank, and when it drops out the engine falls back to a fixed assumption that can hurt cold starts and driveability, especially on high-ethanol blends.
Read this codeFuel Composition Sensor Circuit Range/Performance
The flex-fuel composition sensor is responding, but its ethanol reading doesn't make sense to the PCM — it's out of the expected range or it isn't moving the way it should after a fuel-up. This is the 'plausibility' version of the flex-fuel sensor codes, a step beyond a simple dead-circuit fault.
Read this codeFuel Composition Sensor Circuit Low
The flex-fuel composition sensor's signal has dropped to the bottom of its range — a circuit-low fault, usually a short to ground, a failed sensor, or a broken signal wire. On a flex-fuel vehicle this is the PCM saying it can no longer read how much ethanol is in the tank.
Read this codeFuel Composition Sensor Circuit High
The flex-fuel composition sensor's signal has climbed to the top of its range — a circuit-high fault, most often an open circuit, a loss of ground, or a failed sensor. It's the mirror image of P0178: the same sensor, same flex-fuel system, but the signal is stuck high instead of low.
Read this codeFuel Temperature Sensor "A" Circuit
The circuit for the first fuel temperature sensor is reporting a value the controller cannot believe. The part is inexpensive; where the manufacturer chose to put it is what decides the bill.
Read this codeFuel Temperature Sensor "A" Circuit Range/Performance
The fuel temperature reading is electrically believable but factually wrong. No meter will condemn it — the test is a comparison against the other temperature sensors after the vehicle has sat overnight.
Read this codeFuel Temperature Sensor "A" Circuit Low Input
Signal voltage is sitting near zero, which the controller decodes as fuel hot enough to boil. On a diesel that false report can make the engine derate, so this is the member of the family most likely to change how the vehicle drives.
Read this codeFuel Temperature Sensor "A" Circuit High Input
Signal voltage is pinned at the reference rail, which means the circuit is open somewhere. The most productive first question is not which meter to reach for — it is what was recently done to the fuel system.
Read this codeFuel Temperature Sensor "A" Circuit Intermittent
The fault vanishes whenever anyone looks for it, so the usual tools are the wrong ones. Freeze frame — what the vehicle was doing the moment it set — is worth more here than an hour with a multimeter.
Read this codeFuel Temperature Sensor "B" Circuit
The bare circuit fault on the second fuel temperature sensor. Before anything else, establish that your vehicle actually has a second one and find out where it sits — the letter is a position, not a part number.
Read this codeFuel Temperature Sensor "B" Circuit Range/Performance
The reading is electrically fine but does not agree with what the rest of the system says fuel temperature should be. The trap is assuming the two sensors are supposed to match — they are not.
Read this codeFuel Temperature Sensor "B" Circuit Low
Signal voltage has fallen near zero, which decodes as impossibly hot fuel. On vehicles where this sensor lives in the tank module, the fuel gauge is the first thing to look at — one bad connector explains both faults.
Read this codeFuel Temperature Sensor "B" Circuit High
Voltage is stuck near the top of the range, which means the circuit is open somewhere. Search it as a route rather than a component — this is usually the longer of the two fuel temperature circuits and length is where opens come from.
Read this codeFuel Temperature Sensor "B" Circuit Intermittent
A fault that comes and goes on a circuit you may not be able to reach. When the sensor is sealed inside the fuel tank, the wiggle test is off the table — correlate the fault against fuel level instead.
Read this codeFuel Rail Pressure Sensor Circuit
A general circuit fault on the fuel rail pressure (FRP) sensor — the PCM can't get a reliable reading from the sensor. This is a sensor/electrical code, not a 'pressure is wrong' code like P0087 or P0088.
Read this codeFuel Rail Pressure Sensor Range/Performance
The fuel rail pressure (FRP) sensor's reading is plausible on its face — not pegged high or low — but it's drifting away from what the PCM expects based on other inputs. This is the 'something's off' code in the FRP sensor family.
Read this codeFuel Rail Pressure Sensor Circuit Low Input
The fuel rail pressure sensor circuit is reading too low — a signal voltage below the expected window. As the low-input counterpart to P0193, this usually points at a short to ground, an open or high-resistance connection, a failed sensor, or a genuine low-fuel-pressure condition. On direct-injection and diesel engines it can trigger reduced-power limp mode, so it's worth diagnosing promptly.
Read this codeFuel Rail Pressure Sensor Circuit High Input
The fuel rail pressure sensor's signal is pegged at the top of its range — usually a short to reference voltage or an open ground. This is the electrical mirror of P0192 (which sets when the signal pegs low) and a very different diagnosis from a real over-pressure condition (P0088).
Read this codeFuel Rail Pressure Sensor "A" Circuit Intermittent/Erratic
Rail pressure is a closed-loop control input, not a correction, so an erratic signal makes the controller chase a number that is not real. The first question is whether the sensor is lying or the pressure genuinely is unstable.
Read this codeEngine Oil Temperature Sensor Circuit
The general circuit code for the engine oil temperature sensor. Two questions come before any testing: does this vehicle actually have one, and is the part you are looking at the temperature sensor or the oil pressure switch sitting next to it?
Read this codeEngine Oil Temperature Sensor Range/Performance
Oil and coolant are supposed to disagree — the controller is watching the shape of the warm-up curve, not a single number. Which is why this is the one code in the block that is often a real oil problem rather than a sensor fault.
Read this codeEngine Oil Temperature Sensor Circuit Low
Signal voltage is near zero, which decodes to oil hot enough to be alarming. This sensor lives in oil and under the car, and those two facts account for most of the shorts that set this code.
Read this codeEngine Oil Temperature Sensor Circuit High
The circuit is open, so the reading sits at the cold extreme. Ask what was serviced recently before you test anything — this sensor threads into a port that gets disturbed at almost every oil change.
Read this codeEngine Oil Temperature Sensor Circuit Intermittent/Erratic
The signal cuts out and recovers. This circuit sees a bigger temperature swing than any other sensor circuit on the vehicle, so heat-soak is the pattern to test for — not vibration.
Read this codeInjector Circuit/Open
The engine computer detected an electrical problem in the fuel injector control circuit — most often a wiring, connector, or injector-coil fault. A cylinder that stops getting fuel will misfire, so it should be diagnosed promptly.
Read this codeInjector Circuit/Open - Cylinder 1
The engine computer detected an electrical fault in the fuel injector control circuit for cylinder 1 — usually the wiring, connector, or injector coil. Cylinder 1 may lose fuel and misfire, so diagnose it promptly.
Read this codeInjector Circuit/Open - Cylinder 2
The module tried to fire the cylinder 2 injector and found no working path. The trap on this code is that the fault is very often thermal, and a cold resistance check will tell you the circuit is perfect while the car is still setting the code.
Read this codeInjector Circuit/Open - Cylinder 3
An electrical fault on the cylinder 3 injector circuit. Most of the wasted effort on this code comes from tests that answer a narrower question than people think they are asking — a flashing noid light and a good ohm reading can both coexist with an injector that never opens.
Read this codeInjector Circuit/Open - Cylinder 4
Statistically the engine in front of you is a four-cylinder, which makes this the one member of the family where you do not need a numbering diagram — and where cylinder 4 sits at the far end of the injector harness, the end where wiring faults concentrate for a physical reason.
Read this codeInjector Circuit/Open - Cylinder 5
This is the first code in the block that cannot appear on a four-cylinder, so the code itself tells you something about the engine. It also lands exactly where cylinder numbering stops being obvious — and it covers two completely different jobs depending on whether the engine is an inline five or a V.
Read this codeInjector Circuit/Open - Cylinder 6
Overwhelmingly a V6 code, and on a transverse V6 half the cylinders live on the rear bank under the cowl where you cannot see or reach them. Which side cylinder 6 lands on decides whether this is a half-hour job or a three-hour one — and whether visual inspection is even available to you.
Read this codeInjector Circuit/Open - Cylinder 7
Cylinder 7 only exists on eight-cylinder-and-up engines, so this is a truck, van, large SUV or V8 car — and the engine has enough injectors that they are driven in groups. Before condemning one, read what the other cylinders in that group are saying.
Read this codeInjector Circuit/Open - Cylinder 8
The engine computer detected an electrical fault in the cylinder 8 fuel injector control circuit — usually wiring, a connector, or the injector coil. Cylinder 8 is the rearmost injector on nearly every V8, so confirm the fault before you start taking the intake off.
Read this codeInjector Circuit/Open - Cylinder 9
An electrical fault in the cylinder 9 fuel injector control circuit. Cylinder 9 only exists on V10 and V12 engines, so the very first thing to confirm is that your engine actually has one — and that the code was read correctly.
Read this codeInjector Circuit/Open - Cylinder 10
An electrical fault in the cylinder 10 fuel injector control circuit. On a V10 this is the rearmost cylinder on one bank — the hottest, least accessible injector on the engine, and the one whose connector fails most often.
Read this codeInjector Circuit/Open - Cylinder 11
An electrical fault in the cylinder 11 fuel injector control circuit. Cylinder 11 exists only on twelve-cylinder engines, which changes both the diagnosis and the economics — these engines often use two control modules, one per bank.
Read this codeInjector Circuit/Open - Cylinder 12
The last slot in the generic per-cylinder injector family, and on the usual numbering convention it names the rearmost cylinder on the second bank — the far end of the harness, the hottest corner of the bay, and the most labour to reach.
Read this codeCold Start Injector 1 Malfunction
A fault in the first cold start injector circuit — an extra injector, separate from the main set, that fires only during a cold crank. The signature symptom is unmistakable: the engine is difficult to start when cold and starts perfectly once it is warm.
Read this codeCold Start Injector 2 Malfunction
A fault in the second cold start injector circuit. Because a second cold start injector is fitted almost exclusively to larger V-configuration and diesel engines, the first useful question is whether your engine has one at all — and if it does, whether both cold start injectors are failing together.
Read this codeEngine Shutoff Solenoid Malfunction
The fuel shutoff solenoid circuit is not behaving as commanded. This is the one component standing between a diesel engine that runs and a diesel engine that stops, so the real symptom is usually a no-start or a run-on rather than a warning light.
Read this codeInjection Timing Control Circuit Malfunction
Commanded and actual injection timing no longer agree. Because the timing advance mechanism is driven by fuel pressure inside the pump, a restricted filter or air in the fuel can set this code without a single bad wire.
Read this codeEngine Coolant Over Temperature Condition
The PCM recorded engine coolant temperature above its safe limit — the engine has actually overheated. This is one of the few codes that genuinely means stop driving: continued operation risks a warped head, blown head gasket, or a seized engine.
Read this codeTransmission Over Temperature Condition
The transmission fluid temperature has exceeded the safe threshold. The ECM/TCM logged an overheating event, which can accelerate fluid breakdown and internal wear if it keeps happening.
Read this codeEngine Overspeed Condition
The PCM recorded engine rpm above the manufacturer's maximum safe limit. Most often the record of a real over-rev — usually a missed downshift — but it can also be a false report from an erratic crankshaft or camshaft position signal.
Read this codeThrottle/Pedal Position Sensor/Switch "B" Circuit Malfunction
The engine computer has detected a fault in the circuit for throttle position sensor B — the backup sensor in the redundant pair that tracks throttle or pedal position. Losing one of the pair breaks the cross-check the computer relies on for safe throttle control, so many vehicles respond with reduced-power mode.
Read this codeThrottle/Pedal Position Sensor/Switch 'B' Circuit Range/Performance
The second throttle or accelerator pedal position sensor is reporting a value that doesn't line up with the other sensors. The check engine light is on and the vehicle may drop into a reduced-power 'limp' mode.
Read this codeThrottle/Pedal Position Sensor/Switch 'B' Circuit Low
The second throttle or accelerator pedal position sensor is sending a signal voltage that is too low — typically near zero. The check engine light is on and the vehicle usually drops into a reduced-power 'limp' mode.
Read this codeThrottle/Pedal Position Sensor/Switch 'B' Circuit High
The second throttle or accelerator pedal position sensor is reporting a voltage above its maximum allowed value — usually pinned near the 5-volt reference. The check engine light is on and the vehicle almost always drops into reduced-power limp mode.
Read this codeThrottle/Pedal Position Sensor/Switch 'B' Circuit Intermittent
The second throttle or accelerator pedal position signal is dropping out, spiking, or going erratic — but not staying wrong. The fault comes and goes, which is exactly what makes this code harder to chase than its always-on siblings.
Read this codeThrottle/Pedal Position Sensor/Switch 'C' Circuit
The third throttle or accelerator pedal position sensor circuit has a general fault. This is the opening code of the 'C' block — non-directional, meaning the module has flagged the circuit without specifying that the signal was too low, too high, or implausible.
Read this codeThrottle/Pedal Position Sensor/Switch 'C' Circuit Range/Performance
The third throttle or accelerator position signal is electrically valid but does not agree with the other position sensors. Nothing is shorted or open — the number is simply wrong relative to what the rest of the system is reporting.
Read this codeThrottle/Pedal Position Sensor/Switch 'C' Circuit Low
The third throttle or accelerator position sensor is reporting a voltage below its minimum allowed value, usually near zero. The check engine light is on and the vehicle typically drops into reduced-power limp mode.
Read this codeThrottle/Pedal Position Sensor/Switch 'C' Circuit High
The third throttle or accelerator position sensor is reporting a voltage above its maximum allowed value, usually pinned near the 5-volt reference. The check engine light is on and the vehicle typically drops into reduced-power limp mode.
Read this codeThrottle/Pedal Position Sensor/Switch 'C' Circuit Intermittent
The third throttle or pedal position channel is glitching rather than failing. This is the least common code in a block that is already uncommon, and that rarity is itself diagnostically useful: it usually means the fault is in wiring shared with the other channels rather than in the 'C' sensor.
Read this codeFuel Pump Primary Circuit Malfunction
The engine computer detected an electrical fault in the circuit that switches the fuel pump on — usually the fuel pump relay, its wiring, or the control wire from the computer. The engine may crank without starting or stall unexpectedly.
Read this codeFuel Pump Secondary Circuit Low
The engine computer commanded the fuel pump on but saw low or no voltage on the pump's power feed. Common causes are a failed relay, a corroded connector, or a shorted pump motor. The engine may crank without starting.
Read this codeFuel Pump Secondary Circuit High
The engine computer saw battery voltage on the fuel pump power feed when the pump should have been off. Usually a stuck-closed relay or a wire shorted to power, which can leave the pump running with the key off.
Read this codeFuel Pump Secondary Circuit Intermittent
The engine computer saw the fuel pump power feed drop out and recover. Nothing is wrong right now, but a loose connector, corroded terminal, or chafed wire is breaking the circuit intermittently — a classic cause of random stalling.
Read this codeTurbocharger/Supercharger Overboost Condition
Boost pressure climbed higher than the PCM commanded and didn't come back down. On modern turbocharged engines, this is almost always a wastegate that won't open — not a damaged turbo, despite how it sounds.
Read this codeTurbocharger/Supercharger Boost Sensor "A" Circuit Malfunction
The boost pressure sensor circuit has an electrical fault — the engine computer can't trust its boost reading, so it typically limits boost to protect the engine.
Read this codeTurbocharger/Supercharger Boost Sensor "A" Circuit Range/Performance
The boost sensor's signal is present but doesn't make sense — it disagrees with other sensors or doesn't respond the way real boost should.
Read this codeTurbocharger/Supercharger Boost Sensor "A" Circuit Low
The boost pressure sensor circuit is reading too low — a signal below the expected window. Despite the 'turbocharger' name, this is a sensor-circuit code: the usual causes are a short to ground, an open or corroded connection, a failed boost/MAP sensor, or a disconnected vacuum/pressure reference. It's worth fixing because the PCM uses boost pressure to manage the turbo, and a bad reading can trigger reduced-power mode.
Read this codeTurbocharger/Supercharger Boost Sensor "A" Circuit High
The boost pressure sensor signal is reading above its expected window. Despite the 'turbocharger' name this is a sensor-circuit code — the usual causes are a short to voltage, an open ground, or a failed sensor, and the PCM will often cut power to protect the engine because it cannot tell a false high reading from real overboost.
Read this codeTurbocharger/Supercharger Boost Sensor "B" Circuit Malfunction
A general fault in the second boost pressure sensor circuit. Sensor "B" only exists on engines with more than one boost sensor — twin-turbo, sequential-turbo, and many modern diesels — so the first job is identifying which physical sensor your engine calls "B".
Read this codeTurbocharger/Supercharger Boost Sensor "B" Circuit Range/Performance
The second boost pressure sensor is reporting a signal that is electrically valid but does not agree with what the module expects. Unlike the circuit codes, this one frequently points at a real air-side problem — a boost leak, a stuck wastegate, or a charge air cooler fault — rather than at the sensor.
Read this codeTurbocharger/Supercharger Boost Sensor "B" Circuit Low
The signal from the second boost pressure sensor has fallen below its valid range. A short to ground, an open in the signal wire, or a missing 5-volt reference all produce this — and the reference is worth checking first, because losing it takes several sensors down at once.
Read this codeTurbocharger/Supercharger Boost Sensor "B" Circuit High
The signal from the second boost pressure sensor has risen above its valid range. A short to voltage will do it, but so will a lost or high-resistance ground — and because the module now believes boost is excessive, this code tends to cut power harder than its circuit-low counterpart.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "A"
A general fault in the wastegate control solenoid circuit — the small electrical valve the PCM uses to command the wastegate open and closed. This is the parent code of the family; P0245 and P0246 are its circuit-low and circuit-high forms, and limp mode is the usual first symptom.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "A" Range/Performance
The wastegate solenoid "A" circuit is electrically healthy, but boost is not following the command. This is the one code in the wastegate family that genuinely points at mechanical problems — a sticking wastegate, a leaking actuator, or a cracked vacuum line — rather than at wiring.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "A" Low
The wastegate control solenoid circuit is reading low — a short to ground or an open. The failure is usually the solenoid itself, its wiring, or a blown fuse, and the car typically drops straight into limp mode because the PCM will not run boost it cannot control.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "A" High
The wastegate control solenoid circuit is reading high — the exact opposite of P0245. That points at a short to voltage or a lost ground rather than a short to ground, and the resulting limp mode is the PCM refusing to run boost it cannot control.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "B"
A general fault in the second wastegate control solenoid circuit. Because a second solenoid only exists on twin-turbo, sequential-turbo, and some diesel applications, the first job is establishing which physical valve your engine calls "B" — and whether it has one at all.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "B" Range/Performance
The second wastegate solenoid is being commanded and responding, but the boost result is outside what the module expects. On a twin-turbo engine this often shows up as one side pulling harder than the other, which live data will reveal long before a parts swap will.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "B" Low
The second wastegate solenoid circuit is reading low — the module expected voltage on it and found none. A short to ground and an open circuit both look identical from the module's side, which keeps the test list short and specific.
Read this codeTurbocharger/Supercharger Wastegate Solenoid "B" High
The module found voltage on the second wastegate solenoid circuit when there should have been none. A short to voltage will do it — but so will a corroded ground on a solenoid that is switched on the ground side, which is the cause most often missed.
Read this codeInjection Pump Fuel Metering Control "A" Malfunction (Cam/Rotor/Injector)
Despite the word "injector" in its name, P0251 is not an injector code. It reports a fault in the injection pump's own internal fuel metering control — the actuator and position sensor that decide how much diesel the pump sends out in the first place.
Read this codeInjection Pump Fuel Metering Control "A" Range/Performance (Cam/Rotor/Injector)
The metering actuator's circuit is electrically fine — the module says so by not setting a circuit code. What it is telling you instead is that the fuel quantity it commanded and the fuel quantity it got are two different numbers, which usually means the pump is being starved rather than broken.
Read this codeInjection Pump Fuel Metering Control "A" Low (Cam/Rotor/Injector)
The module found the metering control circuit sitting lower than it should be. A short to ground and an open circuit both look identical from the module's side, which is exactly why the test list for this code is short, blunt, and does not require you to guess which one you have.
Read this codeInjection Pump Fuel Metering Control "A" High (Cam/Rotor/Injector)
The module found voltage on the metering control circuit when there should have been none, or found it refusing to drop when commanded. A short to voltage will do that — but so will a corroded ground on an actuator the module switches from the ground side, and that is the cause most often missed.
Read this codeInjection Pump Fuel Metering Control "A" Intermittent (Cam/Rotor/Injector)
On nearly every engine that sets this code, "A" is the only fuel metering control there is. That absence of a second channel to compare against is the defining constraint here — with no live reference available, the vehicle's own record of past events becomes the diagnostic instrument.
Read this codeInjection Pump Fuel Metering Control "B" (Cam/Rotor/Injector)
This is the second fuel metering control channel — and a second one is not standard equipment. Before you buy anything, establish that your engine has a "B" metering control at all and which physical component your manufacturer means by it, because the answer differs by platform.
Read this codeInjection Pump Fuel Metering Control "B" Range/Performance (Cam/Rotor/Injector)
The second metering channel's circuit is electrically sound — the module said so by not setting a circuit code. What it is reporting is that commanded fuel quantity and actual fuel quantity have diverged. On a two-channel engine, that gives you a diagnostic advantage the "A" code does not have.
Read this codeInjection Pump Fuel Metering Control "B" Low (Cam/Rotor/Injector)
Circuit low on the second metering channel. The useful advantage here is that the healthy "A" channel is sitting on the same engine — which gives you a known-good reference for coil resistance, connector condition, and commanded behaviour that no generic specification chart can match.
Read this codeInjection Pump Fuel Metering Control "B" High (Cam/Rotor/Injector)
The module found voltage on the second metering control circuit when there should have been none, or found it refusing to drop when commanded. The unusual advantage on this code is that the healthy "A" circuit is sitting on the same engine, giving you a live reference for what a correctly behaving circuit looks like.
Read this codeInjection Pump Fuel Metering Control "B" Intermittent (Cam/Rotor/Injector)
There is no standard part called the "B" metering control — it means whatever second element that particular engine uses, and the candidates are physically unlike each other. Identify it from service data before ordering anything or opening anything, because guessing sends you to the wrong end of the engine.
Read this codeCylinder 1 Injector Circuit Low
The engine computer saw the cylinder 1 fuel injector control circuit read low — usually a wire shorted to ground or a shorted injector coil. Cylinder 1 typically misfires, so diagnose it before the catalytic converter is damaged.
Read this codeCylinder 1 Injector Circuit High
An open or voltage-shorted control circuit on the number one injector. Cylinder 1 sits under the front of the engine on most layouts, so this is the injector connector that gets rained on by a weeping water pump or front seal — check for oil and coolant staining before condemning anything.
Read this codeCylinder 1 Contribution/Balance Fault
The engine computer measured how hard each cylinder pushes the crankshaft and found cylinder 1 pulling less than its share. This is a weak-cylinder code, not a wiring code — the cause can be fuel, spark, or compression.
Read this codeCylinder 2 Injector Circuit Low
The engine computer saw the cylinder 2 fuel injector control circuit read low — usually a wire shorted to ground or a shorted injector coil. Cylinder 2 typically misfires, so diagnose it before the catalytic converter is damaged.
Read this codeCylinder 2 Injector Circuit High
Cylinder 2 is the first cylinder whose location is genuinely ambiguous — cylinder 1 defines bank 1, but manufacturers disagree about where number two goes. On a transverse V engine it can be on the far bank, which changes the job from twenty minutes to most of a day.
Read this codeCylinder 2 Contribution/Balance Fault
Cylinder 2 is producing less power than the rest, measured by watching crankshaft speed after each power stroke. Fuel, spark, or compression can all cause it — test before replacing parts.
Read this codeCylinder 3 Injector Circuit Low
The engine computer saw the cylinder 3 injector control circuit reading low — normally a wire shorted to ground or a shorted injector coil. Cylinder 3 usually misfires, so fix it before the catalytic converter suffers.
Read this codeCylinder 3 Injector Circuit High
The cylinder 3 injector control circuit read high — normally an open circuit or a short to battery voltage. Cylinder 3 gets little or no fuel, so expect a misfire and address it promptly.
Read this codeCylinder 3 Contribution/Balance Fault
Cylinder 3 is contributing less power than the other cylinders, measured through crankshaft speed. The cause can be a weak injector, weak spark, or lost compression — testing tells you which.
Read this codeCylinder 4 Injector Circuit Low
The cylinder 4 injector control circuit is being pulled toward ground when it should be floating. Cylinder 4 is the one cylinder position that exists on essentially every modern engine, and on the four-cylinder majority it sits at the far end of both the engine and the injector harness — which shapes where this fault usually is.
Read this codeCylinder 4 Injector Circuit High
The cylinder 4 injector control wire stayed high when the module tried to pull it down — an open circuit or a short to power. Before testing, find out whether this engine fires its injectors individually or in pairs, because on a four-cylinder that changes what the code means.
Read this codeCylinder 4 Contribution/Balance Fault
Cylinder 4 was named as the weak one by a comparison against the other cylinders. On a four-cylinder engine that comparison has only three others to average against, which makes it easier to distort than most people assume.
Read this codeCylinder 5 Injector Circuit Low
The injector drive circuit for cylinder 5 is being pulled low when it should be released. The first job is not testing — it is confirming which injector is actually number 5, because it is rarely the fifth one you can see.
Read this codeCylinder 5 Injector Circuit High
The cylinder 5 injector control circuit measured high — an open circuit or a short to power. The number itself is the trap: cylinder 5 lands on opposite sides of the engine depending on whose numbering convention the manufacturer follows.
Read this codeCylinder 5 Contribution/Balance Fault
Cylinder 5 is contributing less work than the rest. On the long inline diesels where this code lives, position five is at the hot end of the block — which gives it mechanical suspects the front cylinders do not have.
Read this codeCylinder 6 Injector Circuit Low
The cylinder 6 injector control circuit read low — usually a wire shorted to ground or a shorted injector coil. On most V6 and V8 engines cylinder 6 sits at the back, where access drives the labor cost more than the part does.
Read this codeCylinder 6 Injector Circuit High
The cylinder 6 injector control circuit read higher than expected — an open circuit or a short to battery voltage. Because it narrows to only two possibilities, it is the faster half of the low/high pair to diagnose.
Read this codeCylinder 6 Contribution/Balance Fault
Cylinder 6 is producing less power than the other cylinders, measured through crankshaft speed. Fuel, ignition and compression all read the same here — and if other cylinders on the same bank are weak too, look at what they share.
Read this codeCylinder 7 Injector Circuit Low
A cylinder 7 code only appears on engines with at least eight cylinders, which changes both the likely vehicle and the likely cause — heat-hardened harness insulation at the back of the bank is disproportionately common here.
Read this codeCylinder 7 Injector Circuit High
The cylinder 7 injector control circuit read higher than expected — an open circuit or a short to battery voltage. Check the injectors' shared power feed before condemning the injector, especially if other cylinders set codes too.
Read this codeCylinder 7 Contribution/Balance Fault
Cylinder 7 is producing measurably less power than the rest, judged by how hard it accelerates the crankshaft. It usually appears before a misfire code does, which makes it an early warning rather than a breakdown.
Read this codeCylinder 8 Injector Circuit Low
The engine computer measured lower-than-expected voltage on the cylinder 8 injector control wire — a short to ground, a shorted injector coil, or a driver fault. Before you touch anything, confirm where cylinder 8 actually is: GM and Ford put it on opposite sides of the engine.
Read this codeCylinder 8 Injector Circuit High
The engine computer saw higher-than-expected voltage on the cylinder 8 injector control wire, meaning the circuit is open or shorted to power. If several injector high codes set at once, check the shared power feed before you buy a single injector.
Read this codeCylinder 8 Contribution/Balance Fault
Cylinder 8 is at the end of its bank on every V8 — end of the fuel rail, end of the injector harness, last in line for everything. Before you condemn the cylinder, check whether it is simply the first place a marginal supply shows up.
Read this codeCylinder 9 Injector Circuit Low
The engine computer measured lower-than-expected voltage on the cylinder 9 injector control wire — a short to ground, a shorted injector coil, or a driver fault. First, though, confirm your engine actually has a ninth cylinder, because this code is also a favourite hiding place for manufacturer-specific reassignments.
Read this codeCylinder 9 Injector Circuit High
The opposite reading to P0285: the computer saw high voltage where it expected the circuit to be pulled down, which points at an open circuit far more often than anything else. On a ten-cylinder engine that matters, because the injector harness is longer and carries more connectors than any V8's.
Read this codeCylinder 9 Contribution/Balance Fault
A ninth cylinder means a V10 or V12 — a small, expensive population where parts are special-order and access is measured in half-days. That changes the method: on this engine you plan one teardown and test everything while you are in there.
Read this codeCylinder 10 Injector Circuit Low
Lower-than-expected voltage on the cylinder 10 injector control wire — a short to ground, a shorted coil, or a driver fault. On a V10 this is the last cylinder on the bank, sitting against the firewall under the cowl, which makes water intrusion a leading suspect and makes testing from the computer end the smart first move.
Read this codeCylinder 10 Injector Circuit High
The computer saw high voltage where it expected the cylinder 10 injector circuit to be pulled down. That means an open far more often than anything else — and on the last injector at the end of the harness, the most likely open is a connector, not a failed part.
Read this codeCylinder 10 Contribution/Balance Fault
Cylinder 10 is producing less power than the rest, measured at the crankshaft. On a ten-cylinder engine the most valuable information is not this code by itself — it is which other contribution codes came with it, because the pattern tells you whether you have one weak cylinder or a shared problem at the back of a bank.
Read this codeCylinder 11 Injector Circuit Low
The engine computer saw lower-than-expected voltage on the cylinder 11 injector control wire — a short to ground, a shorted injector coil, or a failed driver. Before any of that, confirm your engine has an eleventh cylinder, because only twelve-cylinder engines do.
Read this codeCylinder 11 Injector Circuit High
The engine computer saw higher-than-expected voltage on the cylinder 11 injector control wire, which almost always means an open circuit. On a twelve-cylinder engine the highest-value early check is the shared power feed — and whether your injectors are ordinary solenoids or piezo units, because that decides how you are allowed to test them.
Read this codeCylinder 11 Contribution/Balance Fault
Cylinder 11 is producing measurably less power than the cylinders it is compared against. This is a performance code, not a wiring code — and on a twelve-cylinder engine, the fact that a balance monitor flagged it at all is stronger evidence than the same code would be on a small engine.
Read this codeCylinder 12 Injector Circuit Low
Lower-than-expected voltage on the cylinder 12 injector control wire — a short to ground, a shorted coil, or a failed driver. Cylinder 12 exists only on twelve-cylinder engines, and on those, the single most useful question is whether anyone has had the top of the engine apart recently.
Read this codeCylinder 12 Injector Circuit High
Higher-than-expected voltage on the cylinder 12 injector control wire, which almost always means an open circuit. The fastest way to narrow it is to decide whether the break is on the shared feed side or the individual control side — the stored code list tells you which, before you touch anything.
Read this codeCylinder 12 Contribution/Balance Fault
Cylinder 12 is producing measurably less power than the cylinders it is compared against. This is the last code in the per-cylinder injector block, and it lands on the engine where guessing costs the most — a V12 has twelve of everything, so the diagnostic discipline that is optional elsewhere is mandatory here.
Read this codeVehicle Overspeed Condition
The powertrain control module recorded the vehicle exceeding the top speed it was calibrated for, and cut fuel to bring it back down. Most of the time this is a record of what someone did, not a fault — but if nobody drove it that fast, the speed signal itself is lying, and that is worth finding.
Read this codeEngine Oil Over Temperature Condition
The engine computer determined that engine oil temperature exceeded its safe limit. Treat this as an engine-threatening condition until proven otherwise — and use the gap between oil temperature and coolant temperature to decide immediately whether you are chasing a cooling system problem or an oil system problem.
Read this codeTurbocharger/Supercharger Underboost Condition
The PCM commanded boost, but the turbo can't deliver it. On Ford EcoBoost and VW/Audi TSI engines, this is one of the most-searched codes — and the cause is usually a boost leak somewhere in the charge piping or a tired wastegate actuator, not a dead turbo.
Read this codeRandom/Multiple Cylinder Misfire Detected
The engine computer detected misfires across multiple cylinders or random cylinders it can't isolate. The check engine light may be flashing, the engine may run rough, and continued driving can damage the catalytic converter.
Read this codeCylinder 1 Misfire Detected
The engine computer detected a misfire specifically in cylinder 1. Diagnosis is more targeted than P0300 — the bad part is on or feeding cylinder 1. The check engine light may be flashing; pull over if it is.
Read this codeCylinder 2 Misfire Detected
The engine computer detected a misfire specifically in cylinder 2. Diagnosis is more targeted than P0300 — the bad part is on or feeding cylinder 2. The check engine light may be flashing; pull over if it is.
Read this codeCylinder 3 Misfire Detected
The engine computer detected a misfire specifically in cylinder 3. Diagnosis is more targeted than P0300 — the bad part is on or feeding cylinder 3. The check engine light may be flashing; pull over if it is.
Read this codeCylinder 4 Misfire Detected
The engine computer detected a misfire specifically in cylinder 4. On a 4-cylinder engine, this is the last cylinder; on V engines, position varies by manufacturer. The check engine light may be flashing; pull over if it is.
Read this codeCylinder 5 Misfire Detected
A misfire isolated to cylinder 5. Unlike the higher-numbered misfire codes, this one is possible on a five-cylinder engine — and on a V6 it is the cylinder where the two common numbering conventions disagree about which bank it lives on.
Read this codeCylinder 6 Misfire Detected
A misfire isolated to cylinder 6 — the far-end cylinder on both inline-six and V6 engines. The part is cheap and the access usually is not, which changes what you should replace while the engine is open.
Read this codeCylinder 7 Misfire Detected
Cylinder 7 is failing to fire cleanly on a measurable share of combustion events. Because only V8 (and a handful of V10/V12) engines have a cylinder 7, this code points you directly at a specific coil, plug, or injector on a known side of the engine.
Read this codeCylinder 8 Misfire Detected
Cylinder 8 — the last cylinder in the firing order on a V8 — is missing combustion events. The diagnosis is cylinder-specific, but cylinder 8 sits at the far back of a bank on most V8 platforms, which has real consequences for what the repair actually costs.
Read this codeCylinder 9 Misfire Detected
Cylinder 9 is missing combustion events. There is no generic advice for this cylinder — it only exists on V10 and V12 engines, and those engines share almost nothing with each other, including how they number their cylinders.
Read this codeCylinder 10 Misfire Detected
Cylinder 10 is missing combustion events. It is the highest-numbered cylinder any production engine reports individually — and on a V10 that means the end of a bank, which is both the hardest place to reach and the first place a bank-wide problem shows up.
Read this codeCylinder 11 Misfire Detected
Cylinder 11 is losing combustion events. Before touching a part, understand that the module never watched cylinder 11 burn — it watched the crankshaft slow down and worked backwards to a cylinder number.
Read this codeCylinder 12 Misfire Detected
Combustion failed repeatedly on cylinder 12. Unlike an injector or coil circuit code, this one reports a result rather than an electrical state — which widens the list of possible causes rather than narrowing it.
Read this codeMisfire Detected With Low Fuel Level
The engine misfired while the tank was nearly empty. This is a condition report, not a component failure — and the most common correct response to it is to put fuel in the car.
Read this codeSingle Cylinder Misfire (Cylinder Not Specified)
One cylinder is misfiring and the module cannot say which one. The inability to name it is not a limitation to work around — it is usually the most informative part of the code.
Read this codeCrankshaft Position System Variation Not Learned
A calibration step has not been completed. Nothing on the car is necessarily broken, no part will fix it, and the usual repair is a scan tool procedure performed under specific conditions.
Read this codeMisfire Detected on Startup (First 1,000 Revolutions)
The PCM detected misfire activity during the first 1,000 revolutions after engine start — short enough that no single cylinder code set, but consistent enough to flag the startup window itself as a problem.
Read this codeRough Road Hardware Not Present
The engine controller expects a rough road input that this vehicle is not supplying. Far more often than not the hardware is fine and the module has been told to look for something the car never had.
Read this codeRough Road Sensor "A" Signal Circuit
The signal from the rough road sensor is outside its valid range. The sensor is an accelerometer bolted to the vehicle structure, and what usually goes wrong with it is the bolting rather than the electronics.
Read this codeRough Road Sensor "B" Signal Circuit
A second rough road input is failing. Before testing anything, establish whether that second input is a physical device on this vehicle or a value arriving over the network from the brake system — the two lead to completely different repairs.
Read this codeIgnition/Distributor Engine Speed Input Circuit
The engine management system has lost confidence in the signal that tells it how fast the crankshaft is turning. The word 'Distributor' in the name is a leftover from the 1990s, and working out whether your engine actually has one is the first thing that decides the repair.
Read this codeIgnition/Distributor Engine Speed Input Circuit Range/Performance
The engine speed signal is arriving, but the pattern of it does not agree with what the module expects. That single distinction moves the likely fault away from the sensor and toward the spinning metal it is reading.
Read this codeIgnition/Distributor Engine Speed Input Circuit No Signal
Nothing at all is reaching the module — not a weak signal, not a noisy one, none. Total absence is the easiest fault in this family to pin down, and which of two sensor types you have decides the entire test sequence.
Read this codeIgnition/Distributor Engine Speed Input Circuit Intermittent
The signal drops out briefly and then comes back, so everything tests perfect in the workshop. Heat is the usual reason, and reproducing the fault deliberately is worth more than any measurement taken on a cold engine.
Read this codeKnock Control System Error
The module ran a self-check on its own knock control function and did not get the answer it expected. This is a fault in the system that listens for detonation, not a report that detonation is happening.
Read this codeKnock Sensor 1 Circuit (Bank 1 or Single Sensor)
The engine computer detected an electrical fault with the knock sensor. Without knock detection, the ECM pulls back ignition timing as a safety measure, which reduces power and hurts fuel economy. The engine still runs, but not at its best.
Read this codeKnock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)
The knock sensor on bank 1 is producing a signal, but it's out of the expected range — too weak, erratic, or not matching engine conditions. Unlike a flat circuit failure, a range/performance fault often points at an aging sensor, a loose mounting, or a contaminated connection. Because the PCM uses knock data to protect the engine, it may pull timing as a precaution, costing some power and economy.
Read this codeKnock Sensor 1 Circuit Low (Bank 1 or Single Sensor)
The knock sensor on bank 1 is reporting signal voltage below the PCM's minimum threshold — meaning the PCM is no longer hearing the engine. Without a working knock sensor, ignition timing defaults to a safer, more conservative map and the engine loses both power and efficiency.
Read this codeKnock Sensor 1 Circuit High (Bank 1 or Single Sensor)
The bank 1 knock sensor signal voltage is pinned at or near the upper threshold — usually because something has shorted the signal wire to the 5V reference, or the sensor itself has failed in a way that pegs its output high. Less common than P0327, and more often a wiring fault than a sensor fault.
Read this codeKnock Sensor 1 Circuit Intermittent (Bank 1 or Single Sensor)
The bank 1 knock sensor signal drops out or goes erratic intermittently rather than failing outright. The engine keeps running, but the PCM pulls ignition timing as a precaution, costing a little power and fuel economy.
Read this codeKnock Sensor 2 Circuit Malfunction (Bank 2)
The bank 2 knock sensor circuit has failed — the PCM is no longer hearing the engine on the side without cylinder 1. On V6 and V8 engines this means half of the engine is operating without knock protection, and the PCM defaults to conservative ignition timing across both banks.
Read this codeKnock Sensor 2 Circuit Range/Performance (Bank 2)
The bank 2 knock sensor is producing a signal that doesn't behave the way the computer expects — present, but implausible or out of the normal range.
Read this codeKnock Sensor 2 Circuit Low Input (Bank 2)
The second knock sensor — the one on bank 2 — is reporting signal voltage below the PCM's minimum threshold. If you've already read about P0327, this is the same failure on the opposite cylinder bank: the PCM has effectively gone deaf on that side and falls back to a conservative timing map.
Read this codeKnock Sensor 2 Circuit High Input (Bank 2)
The bank-2 knock sensor is reporting signal voltage above the PCM's maximum threshold — the opposite electrical fault from P0332. Where 'low input' usually means a short, 'high input' typically points to an open circuit: a broken wire, an unplugged connector, or a sensor that's gone open internally.
Read this codeKnock Sensor 2 Circuit Intermittent (Bank 2)
The bank 2 knock sensor signal is cutting in and out — a classic loose-connection or chafed-wire fault rather than a cleanly dead sensor.
Read this codeCrankshaft Position Sensor "A" Circuit
The engine computer isn't getting a usable signal from the crankshaft position sensor. The engine may not start, may stall while driving, or may run intermittently — the crank sensor is critical for ignition and fuel injection timing.
Read this codeCrankshaft Position Sensor "A" Circuit Range/Performance
The crankshaft position sensor is producing a signal, but it's an implausible one — the pulse count, spacing, or amplitude doesn't match what the engine should be doing. Because the crank sensor is the master timing reference, a range/performance fault often shows up as intermittent stalling or hard starting, and the usual culprit is a damaged reluctor (tone) wheel or a sensor air-gap problem rather than a flat-dead circuit.
Read this codeCrankshaft Position Sensor "A" Circuit Low Input
The crankshaft position sensor circuit is reading too low — the voltage the PCM sees has fallen below the expected window, often pointing at a short to ground, an open circuit, or a failed sensor. Because the crank signal is the engine's primary timing reference, a low-input fault frequently means a no-start or stall, and the fix usually lives in the sensor, its connector, or the wiring rather than deep in the engine.
Read this codeCrankshaft Position Sensor "A" Circuit High Input
The crankshaft position sensor circuit is reading too high — the voltage the PCM sees has climbed above its expected window, which typically points at a short to voltage, a wiring fault, or a failed sensor. As the mirror image of the low-input code P0337, it carries the same stakes: because the crank signal is the engine's master timing reference, a high-input fault commonly means no-start or stalling.
Read this codeCrankshaft Position Sensor "A" Circuit Intermittent
The crankshaft position signal cuts out momentarily and then returns. Because the crank sensor is the engine's master timing reference, even a brief dropout can cause a sudden stall, a no-start, or a hard-to-reproduce hesitation — treat it as a stranding risk.
Read this codeCamshaft Position Sensor "A" Circuit (Bank 1 or Single Sensor)
The engine computer detected a circuit fault with the camshaft position sensor. The engine may hard-start, run rough, or refuse to start — the cam sensor tells the ECM which stroke each cylinder is on for fuel injection timing.
Read this codeCamshaft Position Sensor "A" Circuit Range/Performance
The camshaft position sensor is producing a signal, but it's not matching what the engine computer expects based on engine speed and crankshaft position. Often points to a stretched timing chain or a worn sensor.
Read this codeCamshaft Position Sensor "A" Circuit Low Input (Bank 1)
The camshaft position sensor circuit on bank 1 is reading too low — the voltage has dropped below its expected window, usually from a short to ground, an open circuit, or a failed sensor. Unlike a crank-sensor fault, many engines can still run on the crankshaft signal alone, so P0342 often shows up as a long crank, a stumble, or reduced power rather than a dead no-start.
Read this codeCamshaft Position Sensor "A" Circuit High Input (Bank 1)
The camshaft position sensor circuit on bank 1 is reading too high — the voltage has climbed above its expected window, usually from a short to voltage, a connector or wiring fault, or a failed sensor. As the mirror of the low-input code P0342, it carries the same milder consequences: because many engines run on the crank signal alone, you'll often see a hard start or stumble rather than a dead no-start.
Read this codeCamshaft Position Sensor "A" Circuit Intermittent (Bank 1)
The bank 1 camshaft signal is dropping out and recovering. The critical question is whether the sensor is failing to read the camshaft, or reading it correctly while the camshaft itself moves — because one is a $200 part and the other is a timing chain.
Read this codeCamshaft Position Sensor 'A' Circuit (Bank 2)
The engine computer lost or received an unreliable signal from the 'A' camshaft position sensor on Bank 2. It can cause hard starting, stalling, or reduced power, and on some engines a no-start.
Read this codeCamshaft Position Sensor 'A' Circuit Range/Performance (Bank 2)
The 'A' camshaft position sensor on Bank 2 is sending a signal, but it's out of range or doesn't line up with the crankshaft. It can cause hard starting, stalling, rough running, or reduced power.
Read this codeCamshaft Position Sensor 'A' Circuit Low (Bank 2)
Voltage on the Bank 2 'A' camshaft sensor signal wire is sitting below the range the engine computer accepts. Usually a short to ground in the harness or a shorted sensor, and it is separable from a bad sensor with one unplug test.
Read this codeCamshaft Position Sensor 'A' Circuit High (Bank 2)
The Bank 2 'A' camshaft sensor signal is stuck at the top of its range. An unplugged connector produces exactly this reading, which makes P0348 the classic code to appear right after other work was done in the area.
Read this codeCamshaft Position Sensor 'A' Circuit Intermittent (Bank 2)
The Bank 2 'A' camshaft signal drops out briefly and then comes back. Nothing is wrong when you go to test it, so this one is diagnosed with recorded data during a drive rather than with a meter in the driveway.
Read this codeIgnition Coil Primary/Secondary Circuit Malfunction
The one ignition coil code that names no cylinder. That omission is the diagnosis: look at what every coil shares — the power feed, the ground, and the loom they all branch from.
Read this codeIgnition Coil 'A' Primary/Secondary Circuit
A circuit fault on the first ignition coil in the manufacturer's mapping — the one code in this family where you can be reasonably confident which cylinder you are being sent to before you open a manual.
Read this codeIgnition Coil 'B' Primary/Secondary Circuit
The engine computer detected a fault in the primary or secondary circuit of ignition coil 'B'. It usually means a bad coil, connector, or wiring on that cylinder, and it often comes with a misfire.
Read this codeIgnition Coil 'C' Primary/Secondary Circuit
A circuit fault on the third coil in the manufacturer's mapping. Before you go looking for it, settle two questions this letter raises and the earlier letters do not: which cylinder it is, and whether it even serves only one.
Read this codeIgnition Coil 'D' Primary/Secondary Circuit
A circuit fault on the fourth coil in the manufacturer's mapping. 'D' is the highest letter the most common engine on the road can produce, and on a transverse four that coil lives at the wettest end of the cylinder head.
Read this codeIgnition Coil 'E' Primary/Secondary Circuit
The fifth coil in the manufacturer's mapping. 'E' is the first letter in this family that cannot come from a four-cylinder engine, and on the engines that can produce it the coil harness has usually split into branches — which is where the fault often is.
Read this codeIgnition Coil 'F' Primary/Secondary Circuit
The sixth coil in the manufacturer's mapping, and the last one a six-cylinder engine can report. On a transverse V6 that coil is usually against the bulkhead — which makes this a labour bill more than a parts bill, and changes the order you should test in.
Read this codeIgnition Coil 'G' Primary/Secondary Circuit
The seventh coil in the manufacturer's mapping. Seven outputs means a V8, and V8s spend their lives towing, hauling and idling — so this is the letter where a coil that passes every bench test still fails on the road.
Read this codeIgnition Coil 'H' Primary/Secondary Circuit
The eighth coil, and the last one a V8 can report. Eight coils bought at the same time and heat-cycled the same number of times do not fail independently — which makes this a question about the set, and about what you buy to replace it.
Read this codeIgnition Coil 'I' Primary/Secondary Circuit
The ninth coil in the manufacturer's mapping — a letter that only exists on engines with nine or more coils. On anything smaller, the first job is not to fix the code but to prove the code is really what your scanner says it is.
Read this codeIgnition Coil 'J' Primary/Secondary Circuit
The tenth coil in the manufacturer's mapping. Ten outputs puts you on a V10 — an engine layout built in small numbers, where parts are dealer-priced and the coil sits at the bottom of a deep valley. Prove the diagnosis before you buy.
Read this codeIgnition Coil 'K' Primary/Secondary Circuit
The eleventh coil in the manufacturer's mapping — twelve-cylinder territory. A V12 is usually two six-cylinder halves with two of nearly everything, and that duplication hands you a perfect known-good reference for every part of the circuit.
Read this codeIgnition Coil 'L' Primary/Secondary Circuit
The twelfth and final letter the standard defines for ignition coils. Being at the end of the enumeration is a fact about the code numbering rather than about any engine, and it has consequences worth knowing before you start.
Read this codeMisfire Detected - Fueling Disabled
This code describes what the engine computer did, not what went wrong. It found a misfire bad enough to threaten the catalytic converter and shut the injector off to protect it — so the dead cylinder you are about to test is dead on purpose.
Read this codeCamshaft Position Sensor 'B' Circuit (Bank 1)
A fault in the second camshaft sensor on Bank 1 — on most dual-overhead-cam engines, the exhaust cam. Losing it rarely stops the engine, but it usually disables exhaust valve timing control.
Read this codeCamshaft Position Sensor 'B' Circuit Range/Performance (Bank 1)
The Bank 1 exhaust camshaft signal is present but arrives at the wrong crank angle. This is the member of the family that is usually a mechanical problem, not an electrical one — chain stretch, phaser wear, or a clogged oil screen.
Read this codeCamshaft Position Sensor 'B' Circuit Low (Bank 1)
Signal voltage on the Bank 1 exhaust camshaft sensor is below the accepted range. Whether the 'A' sensor on the same bank is also complaining is the fastest way to split a shared-circuit fault from a sensor-specific one.
Read this codeCamshaft Position Sensor 'B' Circuit High (Bank 1)
Signal voltage on the Bank 1 exhaust camshaft sensor is stuck at the top of its range, meaning an open circuit. Water intrusion is a disproportionate cause here, because of where this particular sensor tends to live.
Read this codeCamshaft Position Sensor 'B' Circuit Intermittent (Bank 1)
The Bank 1 exhaust camshaft signal comes and goes. What it drops out of is exhaust valve timing, so the codes that appear alongside it usually identify the fault faster than testing the sensor circuit does.
Read this codeTiming Reference High Resolution Signal 'A' Malfunction
Some engines take two crankshaft references — a coarse one and a fine one. This code is about losing the fine one, and the jobs that depend on it are not the ones most people expect.
Read this codeTiming Reference High Resolution Signal 'A' Too Many Pulses
The module counted more timing pulses per revolution than the engine can physically produce. Extra pulses have to come from somewhere, and the sensor is usually not the somewhere.
Read this codeTiming Reference High Resolution Signal 'A' Too Few Pulses
Pulses are going missing from the fine timing reference. Unlike most sensor codes, the expensive answer here is the toothed wheel, not the sensor reading it.
Read this codeTiming Reference High Resolution Signal 'A' Intermittent/Erratic Pulses
The fault that is never there when you look. This code is diagnosed by capturing an event, not by testing a component — and the freeze frame is worth more than an hour under the bonnet.
Read this codeTiming Reference High Resolution Signal 'A' No Pulses
Nothing at all is arriving on the fine timing reference. It usually means a no-start — and counterintuitively, that makes it the easiest code in this family to diagnose.
Read this codeTiming Reference High Resolution Signal 'B' Malfunction
There is a second fine timing reference, and on many vehicles it is not a second sensor at all — it is a copy of the first one being passed between modules.
Read this codeTiming Reference High Resolution Signal 'B' Too Many Pulses
Extra edges on the second timing channel. Because 'B' usually travels the long way round the engine bay, this is a noise problem far more often than a hardware one.
Read this codeTiming Reference High Resolution Signal 'B' Too Few Pulses
Pulses arriving short on the second channel while the first is perfect. That combination rules out the reference wheel entirely and turns this into a voltage problem, not a timing one.
Read this codeTiming Reference High Resolution Signal 'B' Intermittent/Erratic Pulses
An unstable second timing channel. Because 'B' is usually generated by electronics rather than by a magnet, the first thing to test is not the signal — it is the power feeding whatever makes it.
Read this codeTiming Reference High Resolution Signal 'B' No Pulses
The second timing reference has gone completely silent. Unlike a dead primary reference, this fault frequently ends at a module rather than a sensor — and the engine may still be running while you diagnose it.
Read this codeGlow Plug / Heater Circuit "A" Malfunction
A fault in the primary glow plug heating circuit on a diesel engine. Because there are six or eight plugs sharing the job, this failure creeps up over years rather than arriving overnight.
Read this codeGlow Plug / Heater Indicator Circuit Malfunction
A fault in the dashboard glow plug indicator circuit — the wait-to-start lamp. The heating elements themselves may be in perfect condition; what has failed is the system's way of telling you about them.
Read this codeGlow Plug / Heater Circuit "B" Malfunction
A fault in the second of two glow plug heater circuits. The letter matters: it tells you this engine splits its preheating load across two switched outputs, and that the healthy half is sitting right there as a reference.
Read this codeGlow Plug Control Module Control Circuit Low
A fault on the low-current command line between the engine computer and the glow plug control module — not in the plugs themselves. When this wire fails, every plug stops at once.
Read this codeGlow Plug Control Module Control Circuit High
The command line to the glow plug control module is stuck at a high voltage. This is the direction that can hold the plugs ON — quietly cooking them and draining the battery rather than leaving them cold.
Read this codeCrankshaft Position Sensor 'B' Circuit Malfunction
Your engine has two crankshaft position sensors, and the second one has a circuit fault. The first task is not testing the sensor — it is working out which of the two sensors on your engine is 'B'.
Read this codeCrankshaft Position Sensor 'B' Circuit Range/Performance
The second crank sensor is sending a signal, but the pattern doesn't add up — and because 'B' often reads the flywheel, the suspect list includes the wheel it is reading, not just the sensor doing the reading.
Read this codeCrankshaft Position Sensor 'B' Circuit Low Input
The second crank sensor's circuit is stuck at a low voltage — a wiring-flavoured complaint, on a sensor whose harness lives in one of the harshest neighbourhoods on the vehicle.
Read this codeCrankshaft Position Sensor 'B' Circuit High Input
The second crank sensor's circuit is pinned above its valid range. Near the bellhousing, the likeliest live wire for it to touch is the starter's battery cable — the biggest unfused conductor on the vehicle.
Read this codeCrankshaft Position Sensor 'B' Circuit Intermittent
The second crank sensor's signal keeps dropping out and coming back. Mounted near the starter and exhaust, this sensor lives in a heat-soak zone that makes 'fails hot, works cool' its defining pattern.
Read this codeCamshaft Position Sensor 'B' Circuit (Bank 2)
The engine control module is not receiving a usable signal from the 'B' camshaft sensor on Bank 2. Because Bank 2 only exists on V and flat engines, this code cannot appear on a healthy inline four or inline six.
Read this codeCamshaft Position Sensor 'B' Circuit Range/Performance (Bank 2)
The Bank 2 exhaust camshaft signal is present but out of position relative to the crankshaft. The fact that it is Bank 2 only is the most useful clue you have — it rules out the primary chain drive.
Read this codeCamshaft Position Sensor 'B' Circuit Low (Bank 2)
Voltage on the Bank 2 exhaust camshaft sensor signal line has fallen below the acceptable threshold. On a V engine this circuit runs down the hot side of the engine, which makes heat-related chafe a leading suspect.
Read this codeCamshaft Position Sensor 'B' Circuit High (Bank 2)
The Bank 2 exhaust camshaft signal line is sitting above its upper limit. This is also the cam sensor position most likely to have been supplied with the wrong or a poor-quality replacement part.
Read this codeCamshaft Position Sensor 'B' Circuit Intermittent (Bank 2)
The Bank 2 exhaust camshaft signal drops out and returns. On a transverse engine, Bank 2 is the bank that swings under torque reaction, so worn engine mounts are a genuine root cause here.
Read this codeEGR Insufficient Flow Detected
The engine computer commanded the exhaust gas recirculation (EGR) valve to open, but the resulting flow was lower than expected. Almost always caused by carbon buildup clogging the EGR passages or a stuck-closed EGR valve.
Read this codeExhaust Gas Recirculation Flow Excessive Detected
The PCM is detecting more EGR flow into the intake than it commanded — usually because carbon buildup has the EGR valve stuck partially open, or the valve seat itself has eroded enough that it can't fully close. This is the mirror of P0401 (insufficient flow), and it's almost always a mechanical EGR cleaning or replacement job.
Read this codeExhaust Gas Recirculation Control Circuit Malfunction
The PCM is detecting a fault in the electrical circuit that drives the EGR valve — not the valve itself, but the wiring, connector, or driver that commands it open and closed. If P0402 is about the valve being mechanically stuck, P0403 is about the electrical side losing its connection to the valve.
Read this codeExhaust Gas Recirculation Control Circuit Range/Performance
The EGR valve is responding to commands, but not the way the PCM expects. The diagnostic question is: is the valve mechanically sticky from carbon, or is the position sensor inside the valve drifting and reporting positions that don't match reality?
Read this codeExhaust Gas Recirculation Sensor 'A' Circuit Low
The EGR valve's position feedback signal is reading too low — pinned near zero volts. This is the position-sensor side of the EGR family, distinct from valve-side mechanical failures: the valve may be moving correctly, but the sensor reporting its position has dropped out.
Read this codeExhaust Gas Recirculation Sensor 'A' Circuit High
The EGR position-feedback signal is reading too high — pinned near the top of its range. This is the high-side mirror of P0405: the valve may be moving correctly, but the 'A' sensor reporting its position has gone open or shorted high, so the PCM no longer trusts the feedback.
Read this codeExhaust Gas Recirculation Sensor 'B' Circuit Low
The EGR 'B' feedback signal is reading too low. On the platforms where this code matters most, Sensor B is a dedicated EGR gas temperature sensor rather than a valve position channel — which is why the primary fix here is the temperature sensor, not the valve.
Read this codeExhaust Gas Recirculation Sensor 'B' Circuit High
The EGR 'B' feedback signal is reading too high — the opposite electrical fault from P0407. On a temperature-sensor design, high voltage reads as impossibly cold and almost always means an open circuit: a broken wire, a disconnected connector, or a sensor that's failed open.
Read this codeExhaust Gas Recirculation Sensor 'A' Circuit
The general circuit fault for the EGR position/feedback sensor 'A' — the PCM sees the circuit as electrically wrong but has not classified it as specifically low or high. It is the catch-all parent of P0405 and P0406.
Read this codeSecondary Air Injection System Malfunction
The secondary air injection system (which briefly pumps fresh air into the exhaust on cold start to warm the catalyst) is not working as expected. Common on European cars and certain GM models — often a failed air pump, and frequently expensive.
Read this codeSecondary Air Injection System Incorrect Flow Detected
The secondary air injection system (which briefly pumps fresh air into the exhaust during cold start to help warm up the catalyst) is not flowing the expected amount of air. Common on European cars and certain GM models — and often expensive to fix.
Read this codeSecondary Air Injection System Switching Valve A Circuit Malfunction
The engine computer detected a fault in the control circuit for the secondary air switching valve — the valve that routes pumped air into the exhaust on cold start. Often a failed solenoid, stuck valve, or wiring fault.
Read this codeSecondary Air Injection System Switching Valve A Circuit Open
The engine computer detected an open electrical circuit to the secondary air switching valve A — the wiring or connector is broken, or the solenoid has failed open. The pumped cold-start air can't be routed into the exhaust.
Read this codeSecondary Air Injection System Switching Valve A Circuit Shorted
The engine computer detected a short in the secondary air switching valve A circuit — the wiring is shorted to ground or power, or the solenoid has failed internally. The pumped cold-start air can't be routed into the exhaust.
Read this codeSecondary Air Injection System Switching Valve B Circuit Malfunction
An electrical fault in the control circuit for the secondary air injection system's "B" switching valve — usually wiring, the valve solenoid, or a relay.
Read this codeSecondary Air Injection System Switching Valve B Circuit Open
The control circuit for secondary air switching valve "B" is open — the computer commands the valve but sees no electrical load at all.
Read this codeSecondary Air Injection System Switching Valve B Circuit Shorted
The control circuit for secondary air switching valve "B" is shorted — the computer sees excessive current or an always-live circuit when it should be off.
Read this codeSecondary Air Injection System Relay A Circuit Malfunction
The engine computer detected an electrical fault in the relay that powers the secondary air injection pump. The pump can't be energized to push cold-start air into the exhaust, so the check engine light is on — but the car still drives normally.
Read this codeSecondary Air Injection System Relay 'B' Circuit Malfunction
The PCM detected an electrical fault in the control circuit for the second secondary air injection relay. Emissions-only — the engine runs normally, but the code will fail an inspection and often signals a corroded relay or connector.
Read this codeCatalyst System Efficiency Below Threshold (Bank 1)
The engine computer detected that the catalytic converter on Bank 1 is not reducing emissions as efficiently as expected. The check engine light is on, but the car is usually still drivable.
Read this codeWarm Up Catalyst Efficiency Below Threshold (Bank 1)
The warm-up catalyst on bank 1 — the small cat mounted close to the engine for fast cold-start emissions control — isn't converting pollutants efficiently anymore. Bank 1 contains cylinder 1, so on most American engines this is the driver-side cat.
Read this codeMain Catalyst Efficiency Below Threshold (Bank 1)
The PCM has decided the main catalytic converter on bank 1 isn't cleaning the exhaust well enough. It's a close relative of the far more common P0420 — same monitor, same two-sensor logic — but the wording points specifically at the main catalyst brick. The honest reality is that a worn converter is the usual answer, but it's worth ruling out a lazy downstream O2 sensor and exhaust leaks first, because those are far cheaper.
Read this codeHeated Catalyst Efficiency Below Threshold (Bank 1)
The efficiency monitor for the heated catalyst on bank 1 has fallen below its threshold. This one is worth understanding before you spend money: it specifically refers to a heated-catalyst design, so on many vehicles the real story is the same converter-efficiency logic as P0420 — but on cars that actually use an electrically heated catalyst, the heater circuit itself can be part of the problem.
Read this codeHeated Catalyst Temperature Below Threshold (Bank 1)
The catalyst on bank 1 did not reach its target temperature within the time the module allows. Read that carefully, because it is the one code in this family that says nothing at all about whether the converter works. It is a complaint about the clock, not about the chemistry.
Read this codeCatalyst Temperature Sensor (Bank 1)
The module cannot make sense of the signal from the catalyst temperature sensor on bank 1. This is the bare circuit code — the one that fires when the reading is not merely wrong but absent or impossible — and it is about a thermometer, not about the converter it is bolted into.
Read this codeCatalyst Temperature Sensor Range/Performance (Bank 1)
The catalyst temperature sensor on bank 1 is reporting a number that is electrically perfectly respectable and physically wrong. Nothing is open, nothing is shorted, and the value is simply not what the rest of the vehicle says the temperature ought to be.
Read this codeCatalyst Temperature Sensor Low Input (Bank 1)
The signal voltage from the bank 1 catalyst temperature sensor has fallen below its allowed floor. The trap in this code is the word low, because on the most common sensor design low voltage does not mean low temperature — it means the scan tool is about to show you an alarming number.
Read this codeCatalyst Temperature Sensor High Input (Bank 1)
The signal voltage from the bank 1 catalyst temperature sensor has risen above its allowed ceiling. On the usual sensor design that corresponds to a converter the module now believes is stone cold, and the cost of that belief is not felt on the road — it is felt at the emissions station.
Read this codeCatalyst Heater Control Circuit (Bank 1)
The circuit that drives the catalyst heater on bank 1 is not behaving as commanded. Every other code in this block watches something; this one drives something. That single difference changes the electrical environment, the test method and the eventual bill.
Read this codeCatalyst System Efficiency Below Threshold (Bank 2)
The engine computer detected that the catalytic converter on Bank 2 is not reducing emissions as efficiently as expected. Same condition as P0420, but for the opposite side of a V-configured engine. The check engine light is on, but the car is usually still drivable.
Read this codeWarm Up Catalyst Efficiency Below Threshold (Bank 2)
The warm-up catalyst on bank 2 — the smaller cat mounted close to the engine for fast light-off during cold starts — isn't reducing emissions efficiently enough. Different from the main cat code (P0420/P0430) in location and failure pattern.
Read this codeCatalyst System Efficiency Below Threshold (Bank 2)
The main catalytic converter on bank 2 has lost enough efficiency that the PCM no longer trusts it to handle the emissions load. Same problem as the widely-searched P0420, just on the opposite side of the engine.
Read this codeHeated Catalyst Efficiency Below Threshold (Bank 2)
This is the bank-2 twin of P0423 — the heated-catalyst efficiency monitor has dropped below threshold, but on the cylinder bank opposite the engine's number-one cylinder. The single most useful thing to know is that 'bank 2' tells you exactly where to look, and that comparing both banks often reveals whether you have a real converter problem or a misleading sensor.
Read this codeHeated Catalyst Temperature Below Threshold (Bank 2)
The catalyst on bank 2 failed to reach its target temperature in the time allowed. Before anything else, notice what the code has already told you for free: your engine has two banks, so whatever heating hardware exists here exists twice, and so does the bill.
Read this codeCatalyst Temperature Sensor (Bank 2)
The module has lost a usable signal from the catalyst temperature sensor on bank 2. The part is cheap and the job might not be, because on most V engines the first cost driver on this code is not the sensor — it is which side of the engine bay it lives on.
Read this codeCatalyst Temperature Sensor Range/Performance (Bank 2)
The bank 2 catalyst temperature sensor is electrically healthy and reporting a number the module does not believe. This is the one code in the family where having a second bank turns a judgement call into a measurement — and also the one where the two banks' real differences can fool you.
Read this codeCatalyst Temperature Sensor Low Input (Bank 2)
The signal voltage from the bank 2 catalyst temperature sensor has fallen below its allowed floor. Wiring faults on a V engine are not distributed evenly, and this code lands on the side whose harness has to make the longest and most hostile journey.
Read this codeCatalyst Temperature Sensor High Input (Bank 2)
The signal voltage from the bank 2 catalyst temperature sensor has gone above its ceiling, which on the usual design means an open circuit. Before testing anything, ask what work was done recently — bank 2's connector is the one that gets unplugged.
Read this codeCatalyst Heater Control Circuit (Bank 2)
The circuit that drives the bank 2 catalyst heater is not doing what it was told. This is the only code in the block that carries real current, and current on the far side of a V engine has to travel a long way — which changes both the fault and the way you test for it.
Read this codeEvaporative Emission Control System Malfunction
A general code indicating a problem with the evaporative emission (EVAP) system. Most often a loose gas cap, a cracked hose, or a faulty purge or vent valve. The car drives normally but will fail an emissions test.
Read this codeEVAP System Incorrect Purge Flow
The EVAP purge system is moving fuel vapor at the wrong rate — too much, too little, or at the wrong time relative to what the PCM commanded. Different from the 'leak' codes (P0440, P0455, P0456) — this one is about flow direction and quantity, not whether the system holds pressure.
Read this codeEvaporative Emission System — Small Leak Detected
The engine computer detected a small leak in the evaporative emission (EVAP) system. The check engine light is on but the car runs normally. The most common cause is a worn gas cap or a small crack in an EVAP hose.
Read this codeEvaporative Emission System Purge Control Valve Circuit
An electrical fault in the EVAP purge valve's control circuit — one of the most common emissions codes, and usually a cheap fix.
Read this codeEvaporative Emission System Purge Control Valve Circuit Open
The EVAP purge valve's control circuit is open — the computer commands the valve and sees no current flow at all.
Read this codeEvaporative Emission System Purge Control Valve Circuit Shorted
The EVAP purge valve's control circuit is shorted — excessive current or an always-energized valve, pointing at a shorted winding or grounded wire.
Read this codeEvaporative Emission System Vent Control Circuit Malfunction
The vent valve in the evaporative emission (EVAP) system has an electrical or mechanical fault. Often caused by a failed vent solenoid or by debris and spider webs clogging the vent — both inexpensive fixes.
Read this codeEvaporative Emission System Vent Control Circuit Open
The engine computer detected an open electrical circuit to the EVAP canister vent valve — the wiring or connector is broken, or the vent solenoid itself has failed open. Usually an inexpensive fix once the open is located.
Read this codeEvaporative Emission System Vent Control Circuit Shorted
The engine computer detected a short in the EVAP canister vent valve circuit — the wiring is shorted to ground or power, or the solenoid has failed internally. Usually an inexpensive fix once the short is located.
Read this codeEVAP Vent Solenoid Control Circuit Malfunction
An electrical fault in the circuit that controls the EVAP vent solenoid — the valve that seals the system closed during leak testing. Different from P0446, which is a performance fault; P0449 is specifically about the wiring or solenoid windings.
Read this codeEvaporative Emission System Pressure Sensor/Switch Malfunction
The engine computer has detected a fault in the EVAP pressure sensor circuit — the sensor that measures pressure and vacuum inside the fuel tank so the computer can test for fuel-vapor leaks. The car drives normally, but the computer loses its ability to run EVAP leak tests until the sensor circuit is fixed.
Read this codeEvaporative Emission System Pressure Sensor/Switch Range/Performance
The EVAP pressure sensor is alive but its signal doesn't make sense — it's erratic, out of range for the conditions, or doesn't respond the way the computer expects during leak tests. This is the 'implausible signal' member of the EVAP pressure sensor family, and it's often a sensor drifting out of calibration or a wiring connection going bad.
Read this codeEvaporative Emission System Pressure Sensor/Switch Low
The fuel tank pressure sensor is sending a signal voltage that is too low. The check engine light is on, but the vehicle almost always drives normally.
Read this codeEvaporative Emission System Pressure Sensor/Switch High
The fuel tank pressure sensor is sending a signal voltage that is too high. The check engine light is on, but the vehicle almost always drives normally.
Read this codeEvaporative Emission System Pressure Sensor Intermittent
The EVAP/fuel tank pressure sensor signal is glitching — momentarily jumping or dropping in ways real tank pressure can't. Usually a connector or wiring fault.
Read this codeEvaporative Emission System — Large Leak Detected
The engine computer detected a large leak in the evaporative emission (EVAP) system. The most common cause is a loose, missing, or damaged gas cap. The car runs normally but will fail an emissions test until the leak is fixed.
Read this codeEVAP System Very Small Leak Detected
The EVAP system has a leak roughly 0.020 inches in diameter — about half the size of P0455's threshold. About 50% of these codes turn out to be the gas cap. The rest can be frustrating to find because the leak is tiny.
Read this codeEvaporative Emission System Leak Detected (Fuel Cap Loose/Off)
The engine computer detected an EVAP leak and specifically identified the fuel cap as the suspected location. Almost always solved by tightening or replacing the gas cap — the cheapest fix in the EVAP family.
Read this codeEvaporative Emission System Purge Control Valve Circuit Low
The control circuit for the EVAP purge valve is reading low voltage — usually a short to ground in the wiring or a shorted purge solenoid. It completes the purge valve circuit family alongside the general circuit code: same valve, but this code tells you which direction the electrical fault leans.
Read this codeEvaporative Emission System Purge Control Valve Circuit High
The control circuit for the EVAP purge valve is reading high voltage — usually an open circuit, a broken wire, an unplugged or failed solenoid, or a short to power. It's the mirror of the circuit-low code: same valve, opposite electrical direction, and the direction is your first diagnostic clue.
Read this codeFuel Level Sensor "A" Circuit
The general circuit fault for the primary fuel level sensor — the module can't get a usable signal from the tank sending unit. The engine runs normally, but the fuel gauge and distance-to-empty reading can't be trusted.
Read this codeFuel Level Sensor 'A' Circuit Range/Performance
The fuel level reading is not falling the way the fuel actually being burned says it should. This is a plausibility code, not a voltage code, and it can set with a perfectly healthy circuit.
Read this codeFuel Level Sensor 'A' Circuit Low
Signal voltage on the fuel level circuit is pinned below its valid range. If the fuel pump module was replaced recently, that is the first thing to investigate — and a pinned reading can also block emissions readiness.
Read this codeFuel Level Sensor 'A' Circuit High
The fuel level signal has gone above its allowed ceiling, which on a resistive sender means the circuit has gone open. The most common physical reason is oddly specific: the resistance track is worn through at the level your tank sits at most of the time.
Read this codeCooling Fan Relay 1 Control Circuit
The PCM has detected an electrical fault in the control circuit for the primary cooling fan relay — usually a failed relay, damaged wiring, or a problem with the fan motor itself.
Read this codeCooling Fan 2 Control Circuit
The engine computer detected an electrical fault in the control circuit for the secondary (fan 2) cooling fan or its relay. The car still drives, but the cooling system has lost part of its capacity, so overheating is a real risk in traffic.
Read this codeCooling Fan 3 Control Circuit
The engine computer detected an electrical fault in the control circuit for a third cooling fan or fan-control stage. The car drives normally, but the cooling system has lost capacity, so overheating becomes a risk in heavy demand.
Read this codeCooling Fan Rationality Check Failed
The engine computer ran a logic check on the cooling fan system and the results didn't add up — the fan's actual behavior doesn't match what the PCM commanded or expected from coolant temperature. The car drives, but the cooling system may not be working correctly.
Read this codeExhaust Gas Recirculation Throttle Position Control Range/Performance
The EGR throttle — an intake throttle plate used to help drive exhaust-gas recirculation flow — isn't moving to the position the PCM commands. Common on diesels and some EGR-heavy gasoline engines, this is usually a carbon-fouled or sticking EGR throttle, an actuator or motor fault, or a wiring/sensor problem. Expect reduced EGR performance, possible limp mode, and a failed emissions test until it's resolved.
Read this codeEvaporative Emission System Flow During Non-Purge Condition
The EVAP system is showing fuel vapor flow when the PCM hasn't commanded the purge valve open — almost always a stuck-open or leaking purge valve letting vapor pass into the engine continuously instead of only during scheduled purge events.
Read this codeEvaporative Emission System Low Purge Flow
The PCM commanded the EVAP purge valve open but didn't see the expected flow of fuel vapor into the intake. Usually a restriction — a clogged purge valve, a blocked line, or a saturated charcoal canister — rather than an electrical fault.
Read this codeEvaporative Emission System Vent Valve Control Circuit Low
The voltage on the EVAP vent valve control circuit is lower than the PCM expects — typically a short to ground, a shorted solenoid winding, or a driver-side fault. The engine runs normally, but the EVAP leak test can't run.
Read this codeEvaporative Emission System Vent Valve Control Circuit High
The voltage on the EVAP vent valve control circuit is higher than the PCM expects — typically an open circuit, an unplugged connector, or a short to power. The engine drives normally, but the EVAP leak test can't run.
Read this codeVehicle Speed Sensor 'A' Malfunction
The powertrain control module isn't getting a usable vehicle-speed signal. On older vehicles that means a failed vehicle speed sensor; on most newer ones, where speed is calculated from the ABS wheel-speed sensors, it often points to a wheel-speed sensor or wiring instead.
Read this codeVehicle Speed Sensor 'A' Range / Performance
The vehicle-speed signal is present but doesn't make sense — it's erratic, drops in and out, or disagrees with what the other sensors say the car is doing. Where P0500 means no signal, P0501 means a signal the PCM can see but can't trust.
Read this codeVehicle Speed Sensor 'A' Circuit Low Input
The vehicle-speed signal is reading persistently low — below what the PCM expects when the car is clearly moving. Where P0500 means no signal at all, P0502 means a weak, suppressed signal that usually points to a short to ground, a dragging sensor, or a high-resistance connection.
Read this codeVehicle Speed Sensor 'A' Intermittent / Erratic / High
The vehicle-speed signal is jumping around, spiking high, or cutting in and out — present one moment and wrong the next. This is the intermittent member of the speed-sensor family, and intermittent faults are the hardest to pin down because they often vanish the moment you go looking.
Read this codeBrake Switch "A"/"B" Correlation
The two signals from the brake pedal switch disagree with each other — the computer can't tell for sure whether you're pressing the brake. Usually the switch itself.
Read this codeIdle Air Control System Malfunction
The idle air control (IAC) valve isn't responding to PCM commands the way it should — idle is rough, hunting, stalling, or running too high. Applies to older pre-electronic-throttle vehicles where a dedicated IAC valve controls idle airflow around a mechanically-cabled throttle.
Read this codeIdle Air Control System RPM Lower Than Expected
The engine is idling slower than the PCM's target RPM and the idle control strategy can't bring it back up — usually a dirty throttle body, a tired idle air control valve, or a vacuum-related restriction.
Read this codeIdle Air Control System RPM Higher Than Expected
The engine is idling faster than the PCM's target RPM and the idle control strategy can't bring it back down — most often a vacuum leak letting extra air past the throttle plate.
Read this codeIdle Air Control System Circuit Low
The PCM measured less voltage on the idle air control valve's control wire than the circuit should ever show — usually the wire is dragged to ground, or the module's own output driver has failed shorted.
Read this codeIdle Air Control System Circuit High
Voltage on the idle air control circuit stayed up when the module tried to pull it down — the classic signature of an open circuit, a burned-out coil, or a lost power feed.
Read this codeClosed Throttle Position Switch
A switch — not a sensor — is supposed to tell the module the throttle is at rest, and its on/off state no longer agrees with what the rest of the throttle data says.
Read this codeIdle Air Control Circuit
The general-purpose fault code for the idle air control circuit — set when the module knows the circuit is wrong but has no separate code to say which direction it went wrong in.
Read this codeStarter Request Circuit
The circuit that asks for a crank is faulty — the module either never received a valid start request, or received one it could not act on. This is a no-crank code, not a running-engine code.
Read this codeIncorrect Immobilizer Key
The vehicle's anti-theft (immobilizer) system did not recognize the key's electronic code. The PCM rejects the key's transponder signature, and as an anti-theft measure it can prevent the engine from starting or running.
Read this codeBattery Temperature Sensor Circuit Range/Performance
The battery temperature reading is electrically fine but does not agree with the other temperature sensors on the vehicle, so the module has flagged it as implausible rather than broken.
Read this codeBattery Temperature Sensor Circuit
The module has lost a credible battery temperature reading, so it can no longer tune charging voltage to how warm or cold the battery actually is — a code about battery lifespan, not about how the car drives.
Read this codeBattery Temperature Sensor Circuit Low
Signal voltage on the battery temperature circuit has collapsed toward zero, which a thermistor circuit reads as "extremely hot" — so the charging system pulls voltage down and quietly undercharges the battery.
Read this codeBattery Temperature Sensor Circuit High
Signal voltage on the battery temperature circuit has risen to the top of its range, which the module reads as a deeply frozen battery — so it raises charging voltage, and in warm weather that can cook the battery.
Read this codeIdle Air Control Circuit Intermittent
The idle air control circuit works when you test it and fails when you are not looking, which makes freeze-frame data and a physical wiggle test far more useful here than any static measurement.
Read this codeIdle Air Control System Performance
The idle air control valve obeys every command it is given and the engine still does not idle where it should, which usually means the module has run its idle adaptation to the end of its travel and has nothing left to give.
Read this codeEngine Oil Pressure Sensor/Switch Circuit Malfunction
The catch-all circuit fault for the oil pressure sensor — the PCM has detected a general problem with the sensor circuit that doesn't land cleanly in the low (P0522) or high (P0523) bucket. As with the rest of this family, the fix is usually a cheap sensor, but the discipline of verifying real pressure first is non-negotiable.
Read this codeEngine Oil Pressure Sensor/Switch Range/Performance
The PCM is seeing an oil pressure value that doesn't match what it expects for the current RPM, temperature, and load — but it's not pegged at zero or maxed out. The question every P0521 diagnosis has to answer first: is the engine actually low on oil pressure, or is the sensor lying?
Read this codeEngine Oil Pressure Sensor/Switch Low Voltage
The PCM is seeing the oil pressure sensor signal pinned at or near zero volts. On GM Vortec V8 trucks this is one of the most-searched codes in existence — and the gauge dropping to zero in the dash is what brings people in. The fix is almost always a $40 sensor.
Read this codeEngine Oil Pressure Sensor/Switch High Voltage
The PCM is seeing the oil pressure sensor signal pinned at or near the 5V reference. This is almost never real oil pressure — it's the inverse of P0522, and it usually catches DIYers off-guard because the dash gauge may be reading abnormally high or maxed out.
Read this codeEngine Oil Pressure Too Low
Unlike the rest of this family, P0524 is not a circuit code — it's the PCM declaring that measured oil pressure is genuinely below what the engine needs. Treat it as a real low-pressure event until a mechanical gauge proves otherwise, and do not keep driving on it.
Read this codeCruise Control Servo Control Circuit Range/Performance
The cruise control servo/actuator isn't responding the way the computer expects — commands go out, but the feedback doesn't match. Cruise usually just stops working.
Read this codeCooling Fan Speed Sensor Circuit
The engine computer isn't getting a valid speed signal back from the cooling fan. On vehicles with variable-speed or PWM-controlled fans, the PCM expects to see how fast the fan is actually spinning, and that feedback is missing or out of range.
Read this codeFan Speed Sensor Circuit Range/Performance
The cooling fan reports a speed, but not the speed it was told to run — and unlike most range/performance codes, the sensor here is more often telling the truth about a fan that has genuinely slowed down.
Read this codeFan Speed Sensor Circuit No Signal
No speed feedback is reaching the module at all — which is exactly what a fan that is not turning would report, so the first move is to look at whether the fan spins, not to test the sensor.
Read this codeFan Speed Sensor Circuit Intermittent
The fan speed signal comes and goes, and it does so in the wettest, saltiest, hottest-running corner of the vehicle — which makes water intrusion and thermal failure the two suspects worth chasing first.
Read this codeA/C Refrigerant Pressure Sensor "A" Circuit
The powertrain module cannot get a believable pressure reading from the air conditioning transducer, so it usually stops granting the compressor permission to run at all.
Read this codeA/C Refrigerant Pressure Sensor "A" Circuit Range/Performance
The pressure transducer is producing a perfectly legal voltage — it just is not moving the way real refrigerant pressure moves, so the module rejects the reading as untrustworthy rather than out of range.
Read this codeA/C Refrigerant Pressure Sensor "A" Circuit Low
Signal voltage from the air conditioning pressure transducer dropped below its floor — which can mean a shorted wire, or can mean the system genuinely has almost no refrigerant left in it.
Read this codeA/C Refrigerant Pressure Sensor "A" Circuit High
Signal voltage from the air conditioning pressure transducer went to the top of its range — nearly always an open ground or a short to the reference wire rather than an actual overpressure.
Read this codeAir Conditioner Refrigerant Charge Loss
One of the few codes in this range that reports a physical fact about the world rather than a suspect circuit: the system has less refrigerant in it than it should, and refrigerant does not get used up — it leaks.
Read this codeA/C Evaporator Temperature Sensor Circuit
The sensor whose whole job is to stop the evaporator freezing has gone electrically silent, and the classic symptom is a paradox: air conditioning that blows cold for ten minutes and then blows almost nothing at all.
Read this codeA/C Evaporator Temperature Sensor Circuit Range/Performance
The evaporator temperature reading is plausible and stable — it simply never gets cold when the compressor runs, which is the one code in this family where replacing the sensor is most likely to be the wrong repair.
Read this codeA/C Evaporator Temperature Sensor Circuit Low
The evaporator temperature signal has collapsed toward zero volts. On the thermistor curve almost every vehicle uses, that translates to a reading the module treats as unrealistically warm — which is exactly the direction that lets the core ice up.
Read this codeA/C Evaporator Temperature Sensor Circuit High
The evaporator signal has drifted up to the reference rail, which the module reads as a core that is already frozen — so it refuses to run the compressor, and the air conditioning stops working on a system that has nothing else wrong with it.
Read this codeA/C Evaporator Temperature Sensor Circuit Intermittent
A fault that comes and goes on the one circuit in the vehicle that sits next to a component designed to produce liquid water — which is why this code has a season, and why the drain tube deserves checking before the sensor.
Read this codeIntake Air Heater "A" Circuit
The general fault code for the intake air heater — a resistive element that can draw more current than anything on the vehicle except the starter motor, which is why its failures are about heat and hardware rather than delicate signal problems.
Read this codeIntake Air Heater "A" Circuit Low
The low-voltage member of the intake heater family, and the one worth taking seriously — the fault that pulls this circuit low is often a relay stuck closed, which leaves a hundred-plus amp heating element energised when nothing is asking it to be.
Read this codeIntake Air Heater "A" Circuit High
Voltage on the heater circuit is sitting high because current is not flowing through it — often not because anything has broken, but because a bolted joint carrying more than a hundred amps has loosened just enough to stop being a connection.
Read this codeIntake Air Heater "A" Circuit Open
The module commanded the heater and detected no current flow whatsoever. On a modified truck the most common explanation is not a failure at all — it is that the heater was physically removed during an intake upgrade and never accounted for.
Read this codeExhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1
A circuit fault on the sensor that guards the turbo and the particulate filter. It does no harm to the engine directly — the harm is what the module stops doing without it, including the regeneration cycle that keeps a several-thousand-dollar filter from plugging.
Read this codeExhaust Gas Temperature Sensor Circuit Low Bank 1 Sensor 1
The signal voltage from the first exhaust temperature sensor has fallen below anything the module can accept. In practice this is usually a wire touching what it was routed alongside, and the giveaway is a regeneration cycle that starts and quits before it finishes.
Read this codeExhaust Gas Temperature Sensor Circuit High Bank 1 Sensor 1
Signal voltage above the acceptable ceiling on the first exhaust temperature sensor. Nearly always an open circuit rather than a short to power, and unlike its low-side twin this one usually announces itself with an immediate loss of power.
Read this codeExhaust Gas Temperature Sensor Circuit Bank 2 Sensor 1
A circuit fault on the exhaust temperature sensor for the second cylinder bank. The first thing worth establishing is whether the engine even has a second bank, and the second is that on most vehicles this is the harder of the two sensors to reach.
Read this codeExhaust Gas Temperature Sensor Circuit Low Bank 2 Sensor 1
Signal voltage below the acceptable floor on the second bank's exhaust temperature sensor. The useful thing about a bank 2 fault is that the vehicle carries a matching sensor on the other side, which turns a specification lookup into a simple side-by-side comparison.
Read this codeExhaust Gas Temperature Sensor Circuit High Bank 2 Sensor 1
Signal voltage above the ceiling on the second bank's exhaust temperature sensor. Whether this code appeared alone or alongside its bank 1 counterpart is the single most informative thing about it, because it decides how far upstream the fault has to be.
Read this codePower Steering Pressure Sensor Circuit
A general electrical fault on the sensor that tells the engine when the steering pump is loading it. Your steering keeps working — what suffers is the idle, and specifically the idle at the moment you turn the wheel hard while barely moving.
Read this codePower Steering Pressure Sensor Circuit Range/Performance
The steering pressure signal is electrically valid but does not make sense against what the vehicle is doing. This is the one code in the family that is regularly set by a healthy sensor reporting an unhealthy hydraulic system.
Read this codePower Steering Pressure Sensor Circuit Low Input
Signal voltage below the acceptable floor on the steering pressure sensor. The failure this code hides most often is not electrical at all — it is power steering fluid that has crept past a seal, into the connector, and then along the inside of the harness.
Read this codePower Steering Pressure Sensor Circuit High Input
Signal voltage pinned at the top of its range on the steering pressure circuit. Most of the time nothing is shorted to power — the circuit is simply open, and an open input on this sensor floats high by design.
Read this codePower Steering Pressure Sensor Circuit Intermittent
The steering pressure signal drops out and comes back rather than sitting wrong. The tell that separates this code from every other intermittent in the engine bay is that it tracks engine speed, not road surface.
Read this codeBrake Booster Pressure Sensor Circuit
A general fault on the sensor that measures vacuum inside the brake booster. It carries an engine code prefix and a brake system consequence, which is an unusual and important combination.
Read this codeBrake Booster Pressure Sensor Circuit Range/Performance
The booster vacuum signal is present and electrically healthy but does not match what the engine is doing. This is the one code in the family that an entirely good sensor sets, and the repair is usually mechanical.
Read this codeBrake Booster Pressure Sensor Circuit Low Input
Signal voltage below the electrical floor on the booster vacuum sensor. Read carefully before acting — on most of these sensors low voltage means high vacuum, so the instinctive interpretation of this code is backwards.
Read this codeBrake Booster Pressure Sensor Circuit High Input
Signal voltage pinned at the ceiling on the booster vacuum sensor. The most valuable thing on this page is the code arithmetic: P0558 arriving alongside an unrelated cowl-area sensor code means one bad ground, not two bad sensors.
Read this codeBrake Booster Pressure Sensor Circuit Intermittent
The booster vacuum signal drops out and returns. Unlike most intermittent faults, this one usually tracks the weather rather than the road — and on a stop-start vehicle it produces a complaint that sounds nothing like a brake problem.
Read this codeSystem Voltage Malfunction
The module has declared its own supply voltage untrustworthy without saying which direction it went. When this code appears in a list with others, it is the one to fix first — most of the rest are downstream symptoms.
Read this codeSystem Voltage Unstable
The supply voltage is moving around more than the module will tolerate. Unstable is not the same as too high or too low, and the test that finds it is one the other system voltage codes never use — an AC reading on a DC system.
Read this codeSystem Voltage Low
The PCM is seeing battery voltage below the threshold needed for normal operation — usually a failing alternator, an aging battery, or a poor connection on the main charging circuit.
Read this codeSystem Voltage High
The PCM is seeing battery voltage above the maximum safe operating range — almost always a failed voltage regulator inside the alternator pushing too much charge into the system.
Read this codeCruise Control Multi-Function Input "A" Circuit
The module could not make sense of the voltage arriving from the cruise control switch assembly. On most vehicles every button on that stalk shares one wire and is identified purely by resistance, which is why one fault can kill all of them — or make the module read the wrong button entirely.
Read this codeCruise Control "On" Signal
The master enable input for cruise control is not behaving. This is the one signal that has to work before any other cruise button matters, and a fault here typically presents as a system that will not wake up at all rather than one that misbehaves.
Read this codeCruise Control "Off" Signal
The cancel input is the one cruise circuit the module treats as a safety function, so a fault here often disables the whole system on purpose. It is also the code most likely to be caused by something that is not a cruise part at all — the brake pedal switch.
Read this codeCruise Control "Resume" Signal
The resume input is faulted. On nearly every vehicle resume and accelerate are two actions on one physical rocker, so this code arriving with P0570 is normally one worn contact rather than two separate faults — and resume is the most-pressed button on the stalk.
Read this codeCruise Control "Set" Signal
The set command is faulted. Before chasing the switch, be aware that Set is the one cruise input a healthy module is allowed to ignore — below a minimum speed, in the wrong gear or with a speed signal it distrusts, refusing to set is correct behaviour, not a fault.
Read this codeCruise Control "Coast" Signal
The deceleration command is faulted. Coast is the least-used button on the assembly, so a fault confined to it is rarely wear — and a coast input stuck asserted is the one cruise fault that produces a real driving complaint rather than a missing feature.
Read this codeCruise Control "Accel" Signal
The accelerate command is faulted. Its telltale is unique in the family: a tap-to-add-one-mph that stops working while press-and-hold still does. On adaptive cruise vehicles the same fault arrives disguised as a radar complaint.
Read this codeCruise Control / Brake Switch "A" Circuit
Almost every brake pedal switch is two switches in one housing that move in opposite directions, and this code is the module reporting that it cannot make sense of the pair. Your brake lights can be completely normal while it is stored.
Read this codeCruise Control / Brake Switch "A" Circuit Low
The vehicle believes your foot is on the brake permanently. The complaint that actually brings these cars in is often a battery that keeps going flat overnight rather than anything to do with cruise control.
Read this codeCruise Control / Brake Switch "A" Circuit High
The module has never once seen you press the brake. Check the brake lamp fuse before you touch the switch — on many vehicles a single blown fuse produces this exact code and costs a dollar to fix.
Read this codeCruise Control System — Vehicle Speed Too High
This is not a circuit fault. It is the module reporting that road speed went above the ceiling it will operate under — so the first question is whether the vehicle really was going that fast, and sometimes the honest answer is yes.
Read this codeCruise Control Input Circuit
On a lot of modern vehicles the cruise switches do not connect to the engine computer at all — they report to another module over the network. The circuit named here may not be a wire, and that changes where you look.
Read this codeCruise Control Input Circuit Low
Count your codes before you pick up a probe. One low reading is a circuit problem; several low readings across unrelated inputs is a ground problem, and replacing switches will not touch it.
Read this codeCruise Control Input Circuit High
The word "high" makes people hunt for stray voltage. It is almost always the opposite — modules deliberately bias these inputs high so that a disconnected wire is recognisable, which makes this an open-circuit code by design.
Read this codeCruise Control Multi-Function Input "A" Circuit Stuck
A stuck button reads as a perfectly legal value, because a pressed button is exactly what it is. The module works this out from how long the press lasted, which is why no meter will ever find it and live data finds it in ten seconds.
Read this codeCruise Control Multi-Function Input "A" Circuit Range/Performance
The reading landed in the gap between two buttons. It is not too high and not too low — it simply does not decode as anything, which is what happens when a resistance drifts partway to its neighbour.
Read this codeCruise Control Multi-Function Input "A" Circuit Low
On a switch where buttons are identified by resistance, a reading that falls does not become silence — it becomes a different button. That is why this fault shows up as cruise control doing something rather than nothing.
Read this codeCruise Control Multi-Function Input "A" Circuit High
Resistance in a joint can only ever add, never subtract. That makes this the connection code of the family — and the cheapest part on the vehicle is the most likely culprit while the most expensive one is what usually gets sold.
Read this codeCruise Control Vacuum Control Circuit/Open
The first question is whether your vehicle has a vacuum servo at all — many modern ones do not. Where it does, this code is resolved by one measurement across two pins, and the answer is either a wire or a sealed part.
Read this codeCruise Control Vacuum Control Circuit Low
Because the module switches this solenoid on its ground side, low is the energised state. A circuit stuck low is a solenoid that is on when nobody asked for it — which is why this one is worth attending to promptly.
Read this codeCruise Control Vacuum Control Circuit High
The module commanded the solenoid on and the line refused to fall. Counter-intuitively, a solenoid drawing too much current produces this code as often as one drawing none, because the driver protects itself by switching off.
Read this codeCruise Control Multi-Function Input "A"/"B" Correlation
Both circuits can measure perfectly and the fault still be real, because the fault is between them. This is the one code here that a wire-by-wire continuity test cannot find — every conductor is intact end to end.
Read this codeCruise Control Vent Control Circuit/Open
The vent valve is deliberately built so that losing power releases the throttle. That fail-safe design is why an open vent circuit is a system that will not engage at all — and why you have a known-good coil sitting right next to it to compare against.
Read this codeCruise Control Vent Control Circuit Low
This is the one fault in the vent block that pushes against the fail-safe rather than with it: a low reading means the vent is being held shut, so vacuum gets trapped in the servo instead of released. How long the throttle hangs before it lets go is a free measurement of how tight your servo is.
Read this codeCruise Control Vent Control Circuit High
Read this code alongside the others in memory before you touch anything. The two servo solenoids usually share one supply, so a high code on both channels is one feed and a high code on this channel alone is this channel — a decision made for free, before the meter comes out.
Read this codeCruise Control Servo Control Circuit/Open
An open is the one fault in the cruise servo block you can find with your eyes instead of a meter. It is also the one that has usually been there far longer than anyone realises, because nobody notices a broken cruise control until the day they want it.
Read this codeCruise Control Servo Control Circuit Low
The load on this circuit is a coil or a motor, and a coil that has partially shorted still measures a believable resistance while drawing current the module was never built to supply. That is why a bench test can pass on a part that is the fault.
Read this codeCruise Control Servo Control Circuit High
This is the code you cannot prove you have fixed without a road test at speed, and it is also the one that most often has to be answered with a decision rather than a repair — because on the vehicles that still use a cruise servo, the part is frequently no longer made.
Read this codeSerial Communication Link Malfunction
The powertrain control module lost communication over one of the serial data links it uses to talk to other modules or internal processors. It's a network/communication fault rather than a sensor problem — wiring, connectors, grounds, and power supply are the usual culprits before the PCM itself.
Read this codeInternal Control Module Memory Checksum Error
The powertrain control module ran a self-check on its own memory and the checksum didn't match what it expected — the data the computer relies on may be corrupted. Often a software/programming issue resolvable with a reflash, sometimes a genuine internal PCM failure.
Read this codeControl Module Programming Error
The powertrain control module detected that its programming or calibration is missing, incomplete, or not correctly loaded. It almost always points to a software/flashing problem rather than a failed sensor — and is frequently fixable by reprogramming the module with the correct calibration.
Read this codeInternal Control Module Keep Alive Memory (KAM) Error
The PCM's Keep Alive Memory — the data it retains between key cycles, like learned fuel trims and idle settings — failed its self-check. Very often caused by a weak battery, a bad ground, or a recently disconnected battery, and frequently fixed with a simple power-side repair.
Read this codeInternal Control Module Random Access Memory (RAM) Error
The PCM detected a fault in its internal RAM — the working memory it uses for live calculations while the engine runs. Unlike the learned-data codes, this points more strongly at the module hardware itself, though power and ground problems should be ruled out first.
Read this codeInternal Control Module Read Only Memory (ROM) Error
The PCM failed a self-check on its Read Only Memory — the permanent storage that holds the program and calibration the computer runs from. ROM faults point strongly at the module hardware or its software image, and usually mean a reflash or a module replacement.
Read this codePCM Processor Fault
The powertrain control module has detected an internal processor or memory fault — the computer that runs your engine has flagged a problem with itself. Rare across most platforms, but unusually common on certain Ford EcoBoost and Chrysler V6 engines where the cause is often a known PCM hardware defect.
Read this codeControl Module Performance
The PCM detected that its internal processor isn't performing as expected — a self-monitoring or rationality check inside the computer failed. It's a broad internal-fault code; power and ground problems are checked first, but it often ends in a reflash or module replacement.
Read this codeControl Module Vehicle Options Error
Nothing on this car is broken. The module is carrying a list of what the vehicle is supposed to be — engine, gearbox, axle ratio, fitted options — and that list no longer matches the hardware. The first diagnostic question is not electrical, it is historical: what changed?
Read this codeFuel Injector Control Module Performance
The fuel injector control module (FICM) — the module that drives the fuel injectors, common on diesels — is not performing as the ECM expects. Injector drive can be affected, causing hard starting, misfire, or a no-start.
Read this codeTransmission Control Module (TCM) Processor
Before anything else, find out where the transmission controller physically lives on your vehicle. A firewall-mounted box, a controller built into the engine module and a mechatronic unit sitting in gearbox fluid are three completely different jobs with three completely different bills.
Read this codeECM / TCM Incompatible
Two modules that are individually in perfect health are refusing to work together because their software does not match. This is a code you cause rather than one you develop, which is why the repair order is written on the invoice from the last visit and not in a wiring diagram.
Read this codeStarter Relay Circuit
The code names the starter, which is why people budget for one. The module never carries starter current — it switches a relay with a fraction of an amp — so the fault this code describes is a signal wire, and a great many of these repairs cost less than an oil change.
Read this codeStarter Relay Circuit Low
This is the direction that can bite. A control line pulled to ground can energise the relay without anybody asking, which means a starter that engages against a running engine — cheap to fix as a wire, expensive to ignore as a flywheel.
Read this codeStarter Relay Circuit High
One reading, two opposite faults. An open control line and a line back-fed from somewhere else both read high, and their fixes have nothing in common — but the driver's complaint tells you which one you have before you pick up a meter.
Read this codeAlternative Fuel Control Module KAM Error
Keep Alive Memory is everything the controller learned about your specific vehicle, and it is held there by battery power with the key off. That is why the leading cause of this code is not the module — it is the power path that keeps the module's memory alive overnight.
Read this codeAlternative Fuel Control Module RAM/ROM Error
Unlike its neighbour, this one really is internal — there is no external power path to blame. But a failed program checksum is not always a failed chip, and the difference between a reflash and a replacement is a phone call rather than a part.
Read this codeGenerator Control Circuit Malfunction
The PCM has detected a fault in the circuit it uses to control the alternator (generator). On modern vehicles the computer regulates charging output, and P0620 means that command-and-feedback link isn't behaving — often a wiring or connector problem, a failing alternator regulator, or the alternator itself. Left unfixed it can mean over- or under-charging, so it's worth diagnosing before the battery pays the price.
Read this codeGenerator Lamp "L" Control Circuit Malfunction
The PCM has flagged a fault in the alternator's "L" (lamp) terminal circuit — the wire tied to the charging warning light and the alternator's turn-on signal. Often this is a wiring or connector issue or a failing alternator regulator rather than a catastrophic charging failure, but because the L terminal both signals charging status and helps excite the alternator, it's worth checking before the battery light becomes a dead battery.
Read this codeGenerator Field "F" Control Circuit Malfunction
The PCM has detected a fault in the alternator's "F" (field) control circuit — the circuit that actually regulates how hard the alternator charges by controlling its field/rotor winding. Because the field circuit is the lever the computer pulls to set charging output, a fault here often shows up as under- or over-charging, and the cause is usually wiring, the alternator's internal regulator, or the alternator itself.
Read this codeGenerator Lamp Control Circuit
The circuit that controls the battery/charging warning lamp has an electrical fault — the lamp may be stuck on, stuck off, or the signal between alternator and dash is broken.
Read this codeFuel Cap Lamp Control Circuit
An electrical fault in the circuit that drives the "check fuel cap" indicator — the message or lamp itself, not necessarily anything wrong with the cap.
Read this codeGenerator Field/F Terminal Circuit Low
The voltage on the alternator's field (F) terminal circuit is reading too low. As the low-voltage member of the generator field-control family, P0625 usually points at a short to ground, an open or high-resistance connection, or a failing alternator regulator. Because the field terminal sets charging output, a low reading here can mean the alternator isn't being driven to charge properly.
Read this codeGenerator Field/F Terminal Circuit High
The voltage on the alternator's field (F) terminal circuit is reading too high — the mirror image of P0625's low condition. As the high-side member of the generator field-control family, P0626 usually points at a short to voltage, a wiring or connector fault, or a failing alternator regulator. Because the field terminal sets charging output, a high reading can coincide with over-charging, which stresses the battery.
Read this codeFuel Pump "A" Control Circuit/Open
The fuel pump control circuit is one of the few systems on a car designed around a crash rather than around convenience — the fail-safe is deliberately to stop the pump. That design decides both what this fault feels like and the order in which you check things.
Read this codeFuel Pump "A" Control Circuit Low
A fuel pump is the hungriest small motor on the vehicle, and a worn one gets hungrier as it dies. That is why this reading is so often a report on the pump's condition rather than on the wiring — and why the fuel level you habitually drive at is a genuine cause.
Read this codeFuel Pump "A" Control Circuit High
On a vehicle that varies pump speed to hold rail pressure, high is not necessarily a wiring word — it can be the controller asking for more because something downstream is losing pressure. That is why the first tool on this code is often a gauge, not a meter.
Read this codeVIN Not Programmed or Incompatible - ECM/PCM
The engine control module's stored vehicle identification number is blank, or does not match what the rest of the vehicle reports. Nothing is broken — this is a configuration state, and the fix is a keyboard rather than a wrench.
Read this codeImmobilizer Key Not Programmed - ECM/PCM
The engine controller did not receive a key code it recognises, so it refused to let the engine run. The usual result is a vehicle that cranks strongly and will not start — and in most cases the security system is working exactly as intended.
Read this codePCM/ECM/TCM Internal Temperature Too High
A control module is measuring its own internal temperature and reporting that it has climbed past the limit it was designed for. The first question is not what failed inside the module — it is where the module lives and what is heating it.
Read this codePower Steering Control Circuit
The engine controller has lost proper communication with whatever manages steering assist. Before any testing begins, you have to establish which of three completely different steering architectures the vehicle uses, because the circuit this code names is a different physical thing in each one.
Read this codePower Steering Control Circuit Low
Voltage on the steering control circuit has fallen below its limit. What makes this one different is that steering assist is the second-largest electrical load in the vehicle after the starter, so a connection that passes every static test can still collapse the moment the wheel is actually turned.
Read this codePower Steering Control Circuit High
Voltage on the steering control circuit is above its allowed ceiling. The trap in this one is that a broken wire and a short to power look identical to the module, and the symptom is often not heavy steering but steering that is far too light at speed.
Read this codeThrottle Actuator Control Range/Performance (Bank 1)
The throttle blade did not go where it was told. This is not a wiring code — it is a mechanical one, and the detail that catches people out is that the module is timing the movement as well as measuring it, so a throttle that arrives late fails just as surely as one that never arrives.
Read this codeThrottle Actuator Control Range/Performance (Bank 2)
A second throttle channel is not tracking its command — but the first question is whether this engine has a second throttle at all, because most vehicles that can set a bank 2 code do not, and on those the code means something else entirely.
Read this codeIntake Air Heater Control Circuit
The module cannot properly drive the intake air heater relay. The unusual thing about this code is that it lives in a system which only ever runs when it is cold, so it can sit stored for months without anyone noticing a single symptom.
Read this codeSensor Reference Voltage "A" Circuit/Open
The module's first five-volt supply rail is not sitting where it should. Because that rail is shared by a whole group of sensors, the list of things that failed at the same moment is effectively a wiring diagram — and reading it is faster than chasing wire.
Read this codeSensor Reference Voltage "A" Circuit Low
The first five-volt sensor supply is sitting below its allowed limit. The number itself is the evidence — how far below five volts the rail has fallen tells you what kind of fault is pulling it down, and one of the possibilities is that the rail is fine and the module's ground is not.
Read this codeSensor Reference Voltage "A" Circuit High
The first five-volt sensor supply is reading above five volts, and a five-volt regulator cannot do that. Something else is feeding the rail — which makes the cause list unusually short, and makes this the one reference code that damages parts while you think about it.
Read this codeA/C Clutch Relay Control Circuit
The module cannot control the small relay that switches power to the air conditioning compressor clutch — a fault in the command wire, not in the compressor itself.
Read this codeA/C Clutch Relay Control Circuit Low
The module is seeing ground on the A/C relay control wire when it has not commanded one — which can leave the compressor engaged whether you want it or not.
Read this codeA/C Clutch Relay Control Circuit High
The module commands the A/C relay on and the control line refuses to come down, so the relay never closes and the compressor never engages — often the cheapest fault in the whole air conditioning system.
Read this codeSensor Reference Voltage "B" Circuit/Open
The module's second five-volt supply rail is out of specification. The interesting question is why a second rail exists at all — the answer is a deliberate safety decision, and it shapes both the symptoms and the diagnosis.
Read this codeSensor Reference Voltage "B" Circuit Low
The second five-volt supply has been pulled below its limit — and because the sensors on that rail so often live on the transmission, transfer case or a differential, the fault frequently arrives at the module connector having travelled there inside a wire from the other end of the vehicle.
Read this codeSensor Reference Voltage "B" Circuit High
The second five-volt rail is reading above its ceiling. Before assuming a short to power, consider that this rail is often lightly loaded and runs beside switching solenoids — so a disconnected wire picking up voltage from its neighbours can produce the same reading as a genuine fault.
Read this codeGlow Plug Control Module Circuit
The engine control module detected a fault in the glow plug control module circuit on a diesel engine. The module that powers the glow plugs isn't responding correctly, which can cause hard cold starts and rough cold running.
Read this codeCylinder 1 Glow Plug Circuit
A fault — usually an open circuit — was detected in the cylinder 1 glow plug circuit on a diesel engine. The most common cause is a failed glow plug or its wiring, affecting cold starting and smooth cold running.
Read this codeCooling Fan 1 Control Circuit Low
The engine computer detected low voltage on the control circuit for the primary cooling fan relay — the circuit is reading near ground when it shouldn't be, pointing to a short to ground or a failed relay. Overheating in traffic is the main risk.
Read this codeCooling Fan 1 Control Circuit High
The engine computer detected high voltage — or an open circuit — on the control circuit for the primary cooling fan relay. The PCM expected the circuit to pull low and it didn't, pointing to an open wire, a failed relay, or a bad connection. Overheating in slow traffic is the main risk.
Read this codeEngine Oil Pressure Control Circuit Stuck Off
On engines with a variable or two-stage oil pump, the PCM commands oil pressure through a control solenoid — and P06DD means that control circuit is stuck in the off/low state and won't switch to the commanded pressure. The usual causes are the oil pressure control solenoid, its wiring or connector, or sludge holding the valve. Because oil pressure feeds lubrication and variable valve timing, it's worth verifying real pressure promptly.
Read this codeTransmission Control System Malfunction
An umbrella code indicating the transmission control module has detected a fault. The transmission may be in limp mode. Drive directly to a repair shop — the underlying transmission code (often P0741 or a P0750-series code) is what tells the real story.
Read this codeTransmission Range Sensor "A" Circuit (PRNDL Input)
The module cannot read a valid gear selection from the transmission range sensor. Because the same sensor is what permits cranking, this is the code behind the classic "won't start in Park but starts in Neutral" complaint.
Read this codeTransmission Range Sensor "A" Circuit Range/Performance
The range signal is electrically valid but does not agree with what the transmission is actually doing. This is the one code in the family whose most common fix is an adjustment rather than a part — and it very often appears immediately after somebody worked on the car.
Read this codeTransmission Range Sensor "A" Circuit Low
A range circuit is reading grounded when it should not be. On a switch-type range sensor, ground is the signal — so "low" almost always means moisture or corrosion has created a path that the switch never intended.
Read this codeTransmission Range Sensor "A" Circuit High
A range circuit stayed at reference voltage when the switch should have pulled it down. This is the mileage-driven failure in the family — contacts that have been wiped several hundred thousand times eventually stop making contact at all.
Read this codeTransmission Range Sensor "A" Circuit Intermittent
The range signal drops out or jumps momentarily and then comes back. Nothing is wrong with it while the vehicle is parked in a workshop, which means this code is diagnosed by capturing it rather than by measuring it.
Read this codeInput / Turbine Speed Sensor Circuit Malfunction
The transmission's input (turbine) speed sensor is reporting an erratic, missing, or impossible signal. This is the sensor that tells the transmission control module how fast the input shaft is spinning after the torque converter — the counterpart to the output speed sensor in P0720.
Read this codeInput / Turbine Speed Sensor Circuit Range/Performance
The input (turbine) speed sensor is sending a signal, but it's an implausible one — present yet wrong, jumpy, or not matching what engine RPM and gear say it should be. Unlike a flat-out no-signal fault, a range/performance code means the PCM is getting data it doesn't believe, which often points at sensor air-gap, reluctor, or fluid issues rather than a dead circuit.
Read this codeInput / Turbine Speed Sensor No Signal
The input (turbine) speed sensor circuit is producing no signal at all while the transmission is clearly turning. Where P0715 covers an erratic or out-of-range reading, P0717 is the total-dropout case — the TCM sees nothing where it should see shaft speed.
Read this codeInput / Turbine Speed Sensor Circuit Intermittent
The input (turbine) speed sensor signal is cutting in and out. The defining word here is 'intermittent' — the sensor works most of the time, then briefly drops out or glitches before recovering. That on-again-off-again behavior makes this the trickiest of the input-speed-sensor codes, because the fault is often gone by the time you go looking for it.
Read this codeTorque Converter/Brake Switch "B" Circuit Low
The transmission control system sees an abnormally low voltage on the brake switch "B" circuit — the signal that tells it when your foot is on the brake. The torque converter clutch may refuse to lock up (or refuse to unlock), and cruise control usually stops working.
Read this codeOutput Speed Sensor Circuit Malfunction
The transmission's output speed sensor is reporting an erratic, missing, or impossible signal. This is the sensor the transmission control module uses to know how fast the output shaft is spinning — without it, the TCM can't shift correctly or know what gear to be in.
Read this codeOutput Speed Sensor Circuit Range/Performance
The output speed sensor — the one that measures how fast power is leaving the transmission toward the wheels — is sending a reading the PCM doesn't believe. It's present but out of range or out of step with vehicle speed and wheel data. Because output speed also feeds the speedometer and ABS on many vehicles, this code can come with a glitchy speedo as a telltale clue.
Read this codeOutput Speed Sensor Circuit No Signal
The transmission is getting no signal at all from the output speed sensor — the reading has gone to zero or flatlined while the car is clearly moving. This is the most clear-cut of the output-speed codes: not a wrong value, but nothing. Expect a dead or frozen speedometer, a transmission that often falls straight into limp mode, and a fault that's usually a broken circuit or failed sensor rather than a subtle calibration issue.
Read this codeOutput Speed Sensor Circuit Intermittent
The output speed signal is dropping out or glitching rather than failing outright. The car may shift perfectly for miles and then bang into limp mode for no obvious reason, with the speedometer twitching or briefly falling to zero. Intermittent codes are about connections and vibration far more often than about a dead sensor.
Read this codeEngine Speed Input Circuit Malfunction
The transmission control module is not getting a usable engine RPM value. This is the broad, unqualified parent of P0726, P0727 and P0728 — it tells you the engine-speed input is bad without telling you how, so both the electrical and the plausibility sides have to be checked.
Read this codeEngine Speed Input Circuit Range/Performance
The transmission control module is receiving an engine speed value, but it does not agree with what the rest of the vehicle's data says the engine must be doing. The signal is present and wrong rather than missing, which points at a degraded sensor, a damaged reluctor ring, or a marginal circuit rather than a clean break.
Read this codeEngine Speed Input Circuit No Signal
No engine speed value is reaching the transmission control module at all — not a wrong number, but nothing. This is the most clear-cut member of the engine-speed-input family and usually means an open circuit, an unplugged connector, or a dead crankshaft position sensor.
Read this codeEngine Speed Input Circuit Intermittent
The engine speed signal reaching the transmission control module keeps cutting out or glitching, then returning to normal. The car drives fine for miles and then bangs a shift or drops into limp mode for no obvious reason. Intermittent faults live in connections and heat far more often than in parts.
Read this codeIncorrect Gear Ratio
The transmission control module detected that the ratio between input and output speed doesn't match the gear it commanded. The check engine light is on and the transmission may slip, shift harshly, or fall into a limited 'limp' mode.
Read this codeGear 1 Incorrect Ratio
The transmission's actual gear ratio in first gear doesn't match what it should be — the PCM compares input and output shaft speeds and sees the wrong relationship. P0731 usually points at internal slipping (worn clutches or bands), low or degraded fluid, a shift solenoid or valve-body problem, or a speed-sensor issue. It often comes with slipping, harsh shifts, or a drop into limp mode, and warrants prompt attention to avoid further transmission damage.
Read this codeGear 2 Incorrect Ratio
Second is the busiest gear in the box — every departure from rest passes through it — so wearing out here first is arithmetic rather than a defect. On many designs second is also held by a band rather than a clutch pack, which is one of the few internal faults that can sometimes be corrected without opening the transmission.
Read this codeGear 3 Incorrect Ratio
On many transmissions third is direct drive, meaning the two shafts should be turning at exactly the same speed. That makes this the one ratio code you can confirm or dismiss in ten seconds with a scan tool and no specification lookup at all.
Read this codeGear 4 Incorrect Ratio
Fourth is where the torque converter clutch locks up on most vehicles, and a slipping converter clutch produces the same shaft-speed mismatch as a slipping gear. That puts a component on the suspect list here that no other gear-ratio code implicates.
Read this codeGear 5 Incorrect Ratio
Fifth is only commanded at sustained speed under light load, so a short test drive never enters it. A shop that reports no fault found after a lap around the block has tested every gear except the one this code is about.
Read this codeReverse Incorrect Ratio
The transmission's actual gear ratio in reverse doesn't match what it should be — the computer compares input and output shaft speeds and sees the wrong relationship. P0736 usually points at internal slipping (worn reverse clutches or bands), low or degraded fluid, a shift solenoid or valve-body problem, or a speed-sensor issue, and often shows up as weak, slipping, or delayed reverse engagement.
Read this codeTCM Engine Speed Output Circuit
The transmission control module isn't getting a usable engine-speed (RPM) signal on the circuit that carries it. Without knowing how fast the engine is turning, the transmission can't pick shift points properly, so expect harsh or erratic shifting.
Read this codeTCM Engine Speed Output Circuit Low
The voltage on the circuit carrying engine speed to the transmission control module is lower than it should be — usually a short to ground or a signal being dragged down. The transmission loses its RPM reference and shift quality suffers.
Read this codeTCM Engine Speed Output Circuit High
The voltage on the circuit that carries engine speed to the transmission control module is stuck higher than expected — usually an open circuit or a short to power. The transmission loses its RPM reference and defaults to firm, mistimed shifting.
Read this codeTorque Converter Clutch Circuit Malfunction / Open
The PCM has found an electrical problem in the torque converter clutch solenoid circuit — usually an open or shorted winding, a bad connector, or damaged wiring. Where P0741 means the clutch isn't locking (a performance fault), P0740 means the circuit that commands it has an electrical fault.
Read this codeTorque Converter Clutch Circuit Performance / Stuck Off
The torque converter clutch isn't locking up when the PCM commands it to — usually a worn TCC solenoid, dirty transmission fluid, or internal wear inside the converter itself.
Read this codeTorque Converter Clutch Circuit Stuck On
The torque converter clutch is staying locked when it should release. The classic giveaway is the engine stalling as you come to a stop — like a manual-transmission car you forgot to declutch — because the engine and transmission can't decouple at idle.
Read this codeTorque Converter Clutch Circuit Electrical
An electrical fault has been confirmed in the torque converter clutch solenoid circuit — typically an open or shorted solenoid winding, a damaged connector, or a wiring fault. It's the explicitly electrical sibling of P0740, and on many vehicles the two are nearly interchangeable.
Read this codeTorque Converter Clutch Circuit Intermittent
The torque converter clutch circuit is faulting intermittently — locking and unlocking erratically, or throwing a fault that comes and goes. Like all intermittent codes, it's the hardest of the TCC family to catch because the problem often isn't present when you go looking for it.
Read this codePressure Control Solenoid "A" Malfunction
The broad catch-all fault for pressure control solenoid A — the solenoid that regulates main line pressure. It can be electrical or hydraulic in origin. Expect harsh or slipping shifts, and often limp mode, until it is diagnosed.
Read this codePressure Control Solenoid "A" Performance or Stuck Off
Solenoid A is normally the main line pressure regulator, so its failure is felt everywhere at once rather than on one shift. Before reading the symptom, find out whether this solenoid is normally high or normally low — the two designs fail in opposite directions.
Read this codePressure Control Solenoid "A" Stuck On
The main line pressure regulator is stuck energized, so hydraulic pressure stays pinned high across the whole transmission. Every shift is affected, the pump is loaded continuously, and the shift adapts need resetting after the repair.
Read this codePressure Control Solenoid "A" Electrical
The purely electrical member of the pressure control solenoid A family — an open, a short, or out-of-spec resistance in the solenoid or its wiring. Start at the coil, the harness, and the transmission case connector, not at the fluid.
Read this codePressure Control Solenoid "A" Intermittent
The pressure control solenoid A fault comes and goes rather than staying present. Static bench-style testing usually passes — this one is found with live data, a wiggle test, and driving the vehicle at operating temperature.
Read this codeShift Solenoid A Malfunction
An electrical or hydraulic fault has been detected in shift solenoid A, the solenoid that controls one of the lower gear shifts on most automatic transmissions.
Read this codeShift Solenoid "A" Performance or Stuck Off
Shift solenoid A is responding to commands electrically, but it isn't doing its hydraulic job — it's stuck off or performing poorly, so a gear doesn't engage when the transmission asks for it. Unlike the electrical code P0753, this is usually a mechanical or hydraulic problem: a stuck valve, varnish, low or dirty fluid, or debris, which is why a fluid service is the cheapest first move.
Read this codeShift Solenoid "A" Stuck On
Shift solenoid A is stuck in its "on" state — hydraulically jammed or electrically held — so the transmission is stuck in the wrong gears or shifting harshly.
Read this codeShift Solenoid "A" Electrical
The electrical fault on the one shift solenoid whose role is nearly universal — and because solenoid A is half of a two-bit gear-selection table, which gears you have left tells you a great deal before any tool comes out.
Read this codeShift Solenoid "A" Intermittent
Solenoid A drops out and comes back. Intermittent solenoid faults are overwhelmingly a temperature story, which is why so many of these are returned as no-fault-found — the vehicle was tested cold, and cold is the one condition under which the fault does not exist.
Read this codeShift Solenoid "B" Malfunction
Shift solenoid B has a fault — electrical, hydraulic, or both. The useful thing to understand is that shift solenoids work in combination: the TCM energizes A, B, and sometimes C in specific on/off patterns to select each gear, so a failed B knocks out the gears that depend on it. That's why P0755 often shows up as the transmission missing or being stuck out of a particular set of gears rather than failing entirely.
Read this codeShift Solenoid "B" Performance or Stuck Off
"Stuck off" does not describe a fixed hydraulic condition, because these solenoids are supplied in both normally-open and normally-closed forms. Until you know which one your transmission has, the road test tells you the opposite of the truth.
Read this codeShift Solenoid "B" Stuck On
Two friction elements applied at once try to hold the gearset at two ratios simultaneously, and what gives way is clutch material. This is the one code in the family where continuing to drive is the expensive decision.
Read this codeShift Solenoid "B" Electrical
An electrical fault on the second solenoid — and the single most valuable thing to check is whether it arrived alone, because P0758 with P0753 almost never means two dead coils.
Read this codeShift Solenoid "B" Intermittent
Solenoid B's circuit is dropping out and recovering. The fault is usually not in the solenoid but at the sealed pass-through where the harness crosses the transmission case — the one point in the circuit with hot fluid on one side and the engine bay on the other.
Read this codeShift Solenoid "C" Malfunction
The third shift solenoid is not behaving as commanded, and the gears that depend on it — usually the top of the range — drop out. The most useful cost fact on this code is that the labour to reach the solenoid dwarfs the part, which changes what you should replace once the pan is off.
Read this codeShift Solenoid "C" Performance or Stuck Off
A shift solenoid does not create pressure — it only routes it. So every symptom of this code can be produced by a tired pump with a perfectly good solenoid, and a line pressure gauge is what tells the two apart.
Read this codeShift Solenoid "C" Stuck On
This is one of very few internal transmission faults you can prove in your hand on a bench. It is also the one where a new solenoid most often sticks in exactly the same place, because the aluminium bore it lives in has worn.
Read this codeShift Solenoid "C" Electrical
The letter with the least agreement behind it — on many transmissions solenoid C is not a simple on/off shift valve at all, which changes both what fails and how you are supposed to test it.
Read this codeShift Solenoid "C" Intermittent
Solenoid C is dropping out and recovering. Before condemning it, count the codes: solenoids in a pack share a supply and a return, so faults on more than one channel are one shared conductor, not several failing solenoids.
Read this codeShift Solenoid "D" Malfunction
A fault on the fourth shift solenoid. Two things make this code different from its lower-lettered siblings: the letter D does not identify the same device across manufacturers, and the transmissions that have one are often built so you cannot buy a single solenoid at all.
Read this codeShift Solenoid "D" Performance or Stuck Off
Shift solenoid D isn't producing the result the transmission commands — it responds electrically but the shift it controls doesn't happen correctly, or the valve is stuck off. This is the performance/hydraulic side of the D-solenoid family, distinct from the electrical code P0768, and it usually calls for a fluid and valve-body check before condemning the solenoid.
Read this codeShift Solenoid "D" Stuck On
A valve that has stayed applied rather than failed to apply — and because a stuck-on element can hold the driveline coupled all the way to a standstill, this is the one solenoid code that can genuinely stall the engine at a red light.
Read this codeShift Solenoid "D" Electrical
The electrical circuit for shift solenoid D is out of spec — an open, a short, or coil resistance the TCM reads as wrong. This is the electrical member of the D-solenoid family, so the diagnosis starts at the coil resistance, wiring, and case connector, not the fluid. It typically shows up as harsh or missing shifts in the gears solenoid D controls, or a drop into limp mode.
Read this codeShift Solenoid "D" Intermittent
The first question on this code is whether your transmission has a solenoid D at all — the SAE letter space runs further than most gearboxes do. The second is where the fault hides: a solenoid serving the upper gears will not misbehave on a road test around town.
Read this codeShift Solenoid "E" Malfunction
The code number itself is a clue about the hardware: a transmission that can report a fifth shift solenoid is a modern multi-speed unit, and on those no single solenoid owns a single gear — which changes how the fault has to be read.
Read this codeShift Solenoid "E" Performance or Stuck Off
The wiring passed and the hydraulics did not. Stuck off means a spring-returned valve is being held where it rests — which makes this a contamination story, and one that is usually worst on a cold morning.
Read this codeShift Solenoid "E" Stuck On
Shift solenoid E is stuck in its applied state — the valve stays energized/open and keeps routing pressure when the transmission wants it off. That holds the gears tied to E applied when they shouldn't be, causing firm engagement, wrong-gear operation, or a shift that won't release. It's usually mechanical sticking from contaminated fluid, so check fluid before condemning the solenoid.
Read this codeShift Solenoid "E" Electrical
The transmission controller has detected an electrical fault — an open circuit, a short, or out-of-spec resistance — in the shift solenoid E circuit. This is the wiring-and-coil side of the E-solenoid family: start at the connector, harness, and solenoid resistance, not the fluid.
Read this codeShift Solenoid "E" Intermittent
The shift solenoid E circuit is cutting in and out — the TCM sees the electrical signal drop away and come back unpredictably, often with heat or vibration. Intermittent codes almost always trace to connections and wiring rather than a cleanly failed part, so this is a wiggle-test and live-data diagnosis.
Read this codePressure Control Solenoid "B" Malfunction
The broad catch-all fault for the second pressure control solenoid. It can be electrical or hydraulic, so the diagnosis starts wide: fluid condition, then the case connector and coil resistance, then the valve body.
Read this codePressure Control Solenoid "B" Performance or Stuck Off
What solenoid "B" actually controls is not standardised — converter clutch apply on one gearbox, a single clutch pack on another, secondary pulley pressure on a CVT. Identify the transmission before diagnosing, because the symptom you have is the clue to which circuit it serves.
Read this codePressure Control Solenoid "B" Stuck On
A secondary pressure control solenoid is stuck applied. Unlike a main line pressure fault, the damage here is localized — which shift or which condition misbehaves is the single most useful clue you have.
Read this codePressure Control Solenoid "B" Electrical
The transmission control module has detected an electrical fault in the circuit for pressure control solenoid B — an open, short, or out-of-range resistance. Expect shift-quality problems and possibly limp mode.
Read this codePressure Control Solenoid "B" Intermittent
Line pressure and the commanded pressure agree some of the time and not the rest. On a solenoid the module modulates continuously, intermittent points at temperature and fluid condition rather than at a broken wire.
Read this codeShift Malfunction
The transmission was told to change gear and the ratio that came out was not the one that was ordered. This code names an outcome, not a part — which makes it the transmission code most often quoted as a rebuild and most often not needing one.
Read this code1-2 Shift Malfunction
The change from first to second did not produce the ratio it was supposed to. Naming the shift names the hardware — and it clears everything the working shifts share, which is most of the transmission.
Read this code2-3 Shift Malfunction
The change from second to third did not produce the expected ratio. On most transmissions this is the first shift that requires one element to let go while another takes hold — and that overlap is what makes it fail differently from the shifts below it.
Read this code3-4 Shift Malfunction
The change from third to fourth did not produce the expected ratio. This is the region where the torque converter clutch usually joins in, which puts a suspect on the list that none of the lower shifts have.
Read this code4-5 Shift Malfunction
The change from fourth to fifth did not produce the expected ratio. The code number itself is evidence: a transmission that can report a 4-5 shift has at least five forward gears, which rules out an entire generation of hardware before you look at anything.
Read this codeShift/Timing Solenoid "A" Malfunction
The controller has a fault with the shift and timing solenoid it calls "A". Note the change of subject from the codes just below this one: P0780 through P0784 name a shift that went wrong. This names a part. That is a different kind of code and it wants a different first move.
Read this codeShift/Timing Solenoid "A" Range/Performance
The shift and timing solenoid answered its command electrically and the transmission did not respond the way it should have. That combination is the point of this code: it is the one in the family that says the wiring is fine and moves the entire investigation to the other side of the coil.
Read this codeShift/Timing Solenoid "A" Circuit Low
The monitored voltage on the shift and timing solenoid circuit is sitting lower than the controller expects. Something is pulling that circuit down, and inside a transmission there is only one thing it can be pulled down to, which narrows this code far more than it first appears.
Read this codeShift/Timing Solenoid "A" Circuit High
The shift and timing solenoid circuit is sitting at supply voltage when the controller expected it to be pulled down. Nothing is loading the circuit, which means the path is broken somewhere — and on this particular circuit there is one connector that decides whether that break costs a hundred dollars or a thousand.
Read this codeShift/Timing Solenoid "A" Circuit Intermittent
The shift and timing solenoid circuit misbehaves and then recovers. The usual answer to an intermittent fault — grab the harness and wiggle it — is unavailable here, because the harness is sealed inside a transmission. What replaces it is temperature, and freeze frame data is the way in.
Read this codeNormal/Performance Switch Circuit Malfunction
The transmission controller cannot read the switch that selects between normal and performance shift patterns. Alone among the codes around it, this one is about a driver input rather than a transmission component — the part is usually on the console, not in the gearbox, and that changes everything about the repair.
Read this codeIntermediate Shaft Speed Sensor "A" Circuit
The controller has a general fault with the sensor watching the transmission's intermediate shaft. This is the third speed sensor on a transmission that has one, and having three speeds instead of two makes a kind of arithmetic available that no two-sensor transmission can offer.
Read this codeIntermediate Shaft Speed Sensor "A" Circuit Range/Performance
The intermediate shaft sensor is reporting a speed the controller does not believe. Before replacing it, consider the possibility that trips people up on every ratio-derived code: the sensor may be telling the exact truth about a transmission that is slipping.
Read this codeIntermediate Shaft Speed Sensor "A" Circuit No Signal
Zero pulses from the intermediate shaft sensor while the transmission is clearly turning. When a circuit tests healthy and still produces nothing, suspicion shifts from the sensing to the thing being sensed — and in the worst case the sensor is right and the shaft is not moving.
Read this codeIntermediate Shaft Speed Sensor "A" Circuit Intermittent
The intermediate shaft speed signal drops out and comes back. Speed sensors fail in a way that surprises people: the weak ones fail at low speed and recover at high speed, so the road test that finds this fault is a crawl around a car park, not a run down the motorway.
Read this codePressure Control Solenoid "C" Malfunction
The transmission's third pressure control solenoid isn't doing its job. This is the broad catch-all code for solenoid C — it doesn't say whether the problem is electrical or hydraulic, so both have to be checked. Expect harsh, delayed, or slipping shifts.
Read this codePressure Control Solenoid "C" Performance or Stuck Off
A pressure solenoid does not decide whether a gear arrives — it decides how hard and how fast. So the complaint is a transmission that still has all its gears and takes them horribly, and whether that means slamming or slipping depends on how this solenoid rests.
Read this codePressure Control Solenoid "C" Stuck On
The module can turn this circuit on and cannot turn it off. That is a loss of authority rather than a loss of function — and it gives you a decisive test the stuck-off code does not have: take the command away and see whether anything changes.
Read this codePressure Control Solenoid "C" Electrical
The transmission control module has detected an electrical fault in the circuit for pressure control solenoid C — an open, short, or out-of-range resistance. Expect shift-quality problems and possibly limp mode.
Read this codeTransmission Fluid Pressure Sensor/Switch "A" Circuit
A general electrical fault was detected in the transmission fluid pressure sensor or switch 'A' circuit. Usually wiring or a failed sensor, though it can occasionally reflect a genuine pressure problem — verify before replacing parts.
Read this codeTransmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance
The transmission fluid pressure sensor or switch 'A' is reading within its electrical range but the value is implausible or doesn't track pressure changes as expected. Often a lazy sensor or wiring, sometimes a real hydraulic issue.
Read this codeTransmission Fluid Pressure Sensor/Switch "A" Circuit Low
The transmission fluid pressure sensor or switch 'A' is sending a signal that's too low — a low voltage the control module reads as out of range. Usually a wiring or sensor problem, though it can reflect genuinely low pressure.
Read this codeTransmission Fluid Pressure Sensor/Switch "A" Circuit High
The transmission fluid pressure sensor or switch 'A' is sending a signal that's too high — a high voltage the control module reads as out of range. Usually an open circuit or wiring problem rather than an actual pressure issue.
Read this codeTransmission Fluid Pressure Low
The transmission control module has detected that hydraulic line pressure is below the minimum it needs to apply the clutches. This is a serious code — low pressure lets the clutches slip and overheat, so avoid driving until it's diagnosed.
Read this codeMotor Electronics Coolant Temperature Sensor Circuit
The sensor that monitors the temperature of a hybrid or EV's motor/power-electronics cooling loop is reporting an implausible or out-of-range signal. The controller uses this reading to protect the inverter, motor, and related electronics from overheating.
Read this codeReplace Hybrid/EV Battery Pack
The hybrid/EV battery management system has determined that the high-voltage battery pack is degraded or has a failing section beyond serviceable limits. This code commonly indicates one or more weak modules in the pack, not necessarily the whole battery.
Read this code4WD Low Switch Circuit / Transmission (Manufacturer Specific)
P1875 is a manufacturer-specific code whose meaning varies by make. On many Ford/Jeep/Suzuki vehicles it's a 4-Wheel Drive Low switch circuit fault; on some GM vehicles it points at a transmission (harsh 1-2 shift) problem. Confirm the definition for your specific vehicle.
Read this codeNOx Trap Efficiency Below Threshold (Bank 1)
The module has decided the NOx trap is no longer storing and releasing what it should. Before you accept that verdict, understand that this is one of the very few aftertreatment codes where the part may be recoverable rather than ruined.
Read this codeNOx Trap Efficiency Below Threshold (Bank 2)
This code can only exist on an engine with two cylinder banks — and that single fact does most of the diagnostic work, because a fault that appears on one bank alone rules out every cause the two banks share.
Read this codeDiesel Particulate Filter Efficiency Below Threshold Bank 1
The engine controller has calculated that the diesel particulate filter is no longer trapping soot the way it should. "Efficiency" here is a maths result derived from pressure and temperature readings — which is why a cheap sensor hose can produce a quote for a very expensive filter.
Read this codeDiesel Particulate Filter Efficiency Below Threshold Bank 2
The controller has calculated that the particulate filter serving bank 2 is no longer doing its job. The first question is not what failed — it is whether your vehicle has a bank 2 at all, because most diesels that set this code do not.
Read this codeIntake Manifold Runner Control Stuck Open (Bank 1)
The flaps inside the Bank 1 intake manifold are parked in their open position and will not swing shut when commanded. The engine feels tired pulling away from a stop but pulls normally at higher revs.
Read this codeIntake Manifold Runner Control Stuck Open (Bank 2)
The runner flaps serving Bank 2 will not move to their commanded closed position. Because a Bank 2 code only exists on a V-configuration engine, there is a second, identical assembly on the other side to compare it against.
Read this codeIntake Manifold Runner Control Stuck Closed (Bank 1)
The Bank 1 runner flaps are jammed in their closed, low-speed position and will not swing open. The car drives acceptably around town and then hits a wall when asked for full power.
Read this codeIntake Manifold Runner Control Stuck Closed (Bank 2)
The Bank 2 runner flaps are held shut and will not open. A one-sided stuck-closed condition is unusual enough that the asymmetry itself narrows the diagnosis considerably.
Read this codeIntake Manifold Runner Control Circuit / Open (Bank 1)
An electrical fault in the Bank 1 runner control output circuit. This one can set with perfectly healthy flaps and a car that drives normally, because the module is watching its own wiring, not the airflow.
Read this codeIntake Manifold Runner Control Circuit Low (Bank 1)
The Bank 1 runner control circuit is reading lower voltage than the module expects, which usually means the wiring has found a path to ground somewhere it should not have.
Read this codeIntake Manifold Runner Control Circuit High (Bank 1)
The Bank 1 runner control circuit is sitting higher than the module expects. Something is holding that wire up toward battery voltage — and on most designs a corroded ground can do it just as easily as a short to power.
Read this codeIntake Manifold Runner Control Circuit / Open (Bank 2)
The module has found no electrical load on the Bank 2 runner control output. Because Bank 1 has its own driver in the same module, a fault confined to one bank tells you a great deal in a single glance.
Read this codeIntake Manifold Runner Control Circuit Low (Bank 2)
The Bank 2 runner control circuit is being pulled toward ground. On a two-bank system the ground it has found is not always the chassis — the neighbouring bank's own control wire is a real possibility.
Read this codeIntake Manifold Runner Control Circuit High (Bank 2)
The Bank 2 runner control circuit is reading high. The single most valuable thing about this code is that the identical circuit on Bank 1 is still working, which gives you a known-good reference for every measurement you are about to take.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit (Bank 1)
A fault in the device that reports where the intake runner flaps are, rather than in the device that moves them. The flaps may be working perfectly — what the module has lost is its ability to prove it.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit Range / Performance (Bank 1)
The runner position sensor is alive and answering, but the answer does not make sense. This is a plausibility verdict rather than an electrical one, which is why a meter on the connector will read perfectly and tell you nothing.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit Low (Bank 1)
The runner position signal is sitting at or near zero volts. Before diagnosing this circuit, read every other code stored — a position sensor runs on a shared reference, and the fault that collapsed it may belong to a completely different sensor.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit High (Bank 1)
The runner position signal is sitting near the top of its range. On a three-wire sensor a high reading usually means the signal has found the reference rather than battery voltage — which sends you looking at the sensor's ground return, not at a power feed.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit Intermittent (Bank 1)
The module caught a fault it can no longer reproduce. Static measurements will read perfect, because a worn position sensor drops out at one particular shaft angle rather than at one particular temperature.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit (Bank 2)
The generic fault code for the bank 2 runner position sensor circuit. Identify which head is bank 2 before you unbolt anything — on most transverse V engines it is the one against the firewall, and the whole cost of this job is decided by that fact.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit Range/Performance (Bank 2)
The bank 2 position signal is electrically healthy but does not agree with what the module expects. On a two-bank engine that expectation includes bank 1's reading — so this code can be set by a signal that is entirely within its own limits.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit Low (Bank 2)
A low signal on the far bank. The bank 2 sensor circuit is the longer harness run of the two and passes through the part of the engine bay most often disturbed during other repairs, which makes damaged wiring a likelier cause here than a failed sensor.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit High (Bank 2)
A high signal on the far bank. Before anything else, check whether the bank 1 high code is stored too — two banks reading high at the same instant is one shared circuit failing, not two sensors that happened to die together.
Read this codeIntake Manifold Runner Position Sensor / Switch Circuit Intermittent (Bank 2)
An intermittent fault on the expensive bank. Because labour is most of the bill on a rear-head sensor, this is the one code in the family where guessing at the part is the wrong move — the diagnosis has to be conclusive before anything is bought.
Read this codeEvaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Circuit
The fuel vapor temperature sensor is not reporting usable data. It costs you nothing in drivability — what it costs you is the evaporative leak test, which stops running, so the vehicle will not reach emissions readiness.
Read this codeEvaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Range/Performance
The sensor is still producing a believable number — it has simply stopped following reality. Nothing you can measure while standing still will show that, which is why this code is caught by watching a curve over time rather than by taking a reading.
Read this codeEvaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Circuit Low Voltage
The signal has fallen to the bottom of its range, which means a copper-to-copper short somewhere. This circuit spends its whole life under the floorpan, so the question is almost always where the loom touched something it should not have.
Read this codeEvaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Circuit High Voltage
The circuit has come apart somewhere rather than touched something. Openings on this sensor cluster around two places — the connector on top of the tank and the sealed pass-through where the wires leave the pump flange — and both of them fail for reasons you can predict.
Read this codeReductant System Performance (Bank 1)
The diesel exhaust fluid (DEF/SCR) system isn't performing as commanded on bank 1. The ECM asked the reductant system to dose DEF, but the result — usually pressure or NOx reduction — didn't meet expectations. Ignored, it can trigger emissions-based speed limits.
Read this codePost Catalyst Fuel Trim System Too Lean (Bank 1)
The downstream oxygen sensor on bank 1 is reporting a persistently lean signal that the PCM can't correct for, even after the upstream fuel trim has done its work. This points at exhaust leaks, sensor problems, or a cat that's letting unburned oxygen pass through.
Read this codePost Catalyst Fuel Trim System Too Rich (Bank 1)
The bank 1 downstream oxygen sensor is reporting a persistently rich signal that the PCM can't correct out. Usually means a contaminated downstream sensor, a cat that's saturated and dumping unburned fuel through, or fuel system issues that don't trip the upstream lean/rich codes.
Read this codePost Catalyst Fuel Trim System Too Lean (Bank 2)
The downstream oxygen sensor on bank 2 is reporting a persistently lean signal. Mechanically identical to P2096 — same diagnosis, same costs — but you're chasing it on the side of the engine that does NOT contain cylinder 1. Bank identification is the first step.
Read this codePost Catalyst Fuel Trim System Too Rich (Bank 2)
The downstream O2 sensor on bank 2 is reporting a persistently rich signal. Same playbook as P2097 — contaminated sensor, leaking injector, stuck EVAP, or fuel pressure issue — but on the side of the engine that doesn't contain cylinder 1.
Read this codeReductant Pressure Too Low
The diesel exhaust fluid (DEF/SCR) system pressure is below the level the ECM needs to dose reductant properly. Without adequate pressure the SCR system can't reduce NOx as required, which can lead to emissions-based power or speed limits.
Read this codeThrottle Actuator 'A' Control Motor Circuit/Open
The engine computer has lost the circuit to the electronic throttle body's motor — the wire is open or the motor isn't there electrically. The throttle can no longer be commanded, so the vehicle drops into a severe reduced-power mode.
Read this codeThrottle Actuator 'A' Control Motor Circuit Range/Performance
The electronic throttle body's actuator motor isn't moving the throttle plate the way the ECM commands. Actual throttle position doesn't track the command, so the ECM flags a range/performance fault and often limits power to protect the engine.
Read this codeThrottle Actuator 'A' Control Motor Circuit Low
Voltage on the electronic throttle motor's control circuit is being dragged low — most often a wire shorted to ground or a shorted motor winding. The ECM cuts throttle control and puts the vehicle into reduced power mode.
Read this codeThrottle Actuator 'A' Control Motor Circuit High
Voltage on the electronic throttle motor's control circuit is higher than the ECM expects — usually a short to a power source. Throttle control is disabled and the vehicle drops into reduced power mode.
Read this codeThrottle Actuator Control System - Forced Idle
The engine control module has locked the engine to idle as a protective response to a throttle control fault. The engine runs but will not accelerate past a fixed low speed. This is a fail-safe declaration, not a broken part — the real fault is in a companion throttle or pedal code.
Read this codeThrottle Actuator Control System - Forced Engine Shutdown
The engine control module judged a throttle control fault severe enough to shut the engine down rather than let it run. The vehicle will stall or refuse to start while the fault is present. This is the highest tier of the throttle fail-safe strategy and is a safety response, not a failed component.
Read this codeThrottle Actuator Control System - Forced Limited Power
The engine control module has restricted how far it will open the throttle as a protective response to a throttle control fault. The car drives, but power is capped. Like its siblings P2104, P2105 and P2110, this is a fail-safe declaration — the real fault is named by a companion code.
Read this codeThrottle Actuator Control Module Processor
The processor that runs the electronic throttle failed its own internal self-test. The module is not reporting a fault out in the wiring — it is reporting that it no longer trusts its own calculations, and it takes authority away from the throttle as a result.
Read this codeThrottle Actuator Control Module Performance
The powertrain control module is watching the throttle actuator control module from the outside and does not like what it sees. The signals coming back are missing, delayed, or implausible — so the module's behavior, not its wiring, is what has been flagged.
Read this codeThrottle/Pedal Position Sensor 'A' Minimum Stop Performance
The module checked where the throttle plate rests when nothing is asking it to open, and the answer was wrong. The 'minimum stop' is the mechanical hard stop that defines fully closed, and this code says the sensor is not reporting the plate sitting there.
Read this codeThrottle Actuator Control System - Forced Limited RPM
The ECM has forced the engine into a limited-RPM mode as a protective response to a throttle actuator control fault. This is a fail-safe (limp mode) that caps engine speed until the underlying throttle problem is fixed.
Read this codeThrottle Actuator Control System - Stuck Open
The throttle plate will not close. The module commanded it shut, watched the position sensors, and the plate stayed open — which is the one throttle fault that can keep making power after you lift off the pedal.
Read this codeThrottle Actuator Control System - Stuck Closed
The throttle plate will not open. The module commanded it to move, watched the position sensors, and the plate stayed shut — so the engine gets only the air it can pull past a closed plate, which usually means a car that idles but will not accelerate.
Read this codeThrottle/Pedal Position Sensor 'B' Minimum Stop Performance
The 'B' sensor is not reporting the correct rest position. The module checked what the sensor reads when nothing is pressing on it and got a value that does not match the learned closed or released position.
Read this codeThrottle/Pedal Position Sensor 'C' Minimum Stop Performance
The 'C' sensor is not reporting the correct rest position. The module checked what the sensor reads when nothing is pressing on it and got a value that does not match the learned closed or released position.
Read this codeThrottle/Pedal Position Sensor 'D' Minimum Stop Performance
The 'D' sensor is not reporting the correct rest position. The module checked what the sensor reads when nothing is pressing on it and got a value that does not match the learned closed or released position.
Read this codeThrottle/Pedal Position Sensor 'E' Minimum Stop Performance
The same rest-position test as P2115, run on the other sensor. The 'E' channel is not reporting the learned value it should read when the pedal is fully released, so the module no longer knows exactly where 'no request' is.
Read this codeThrottle/Pedal Position Sensor 'F' Minimum Stop Performance
The rest-position check failed on the 'F' sensor — a third position channel that only some vehicles have. Confirming that your platform even uses an 'F' sensor, and where it lives, is the first real step rather than an afterthought.
Read this codeThrottle Actuator Control Motor Current Range/Performance
The engine control module is monitoring how much current the throttle motor draws and does not like what it sees. Unlike the circuit codes, this one is about the amount of current, not the presence of it — which usually means the motor is fighting something, or is worn out inside.
Read this codeThrottle Actuator Control Throttle Body Range/Performance
The throttle plate is not going where the engine control module told it to go. The circuit is fine and the motor is trying — the plate is simply not landing at the commanded position, which points at the throttle body itself rather than at its wiring.
Read this codeThrottle/Pedal Position Sensor 'D' Circuit
The general circuit fault for the 'D' sensor inside the accelerator pedal assembly. It is the unqualified parent of P2121, P2122 and P2123 — it says the signal is unacceptable without saying whether it is too high, too low, or simply implausible.
Read this codeThrottle/Pedal Position Sensor 'D' Circuit Range/Performance
The 'D' pedal sensor is producing a signal that is present and within its electrical limits, but does not make sense — a flat spot, a glitch, or a value that does not match the other pedal sensor. This is the hardest of the family to catch, because a static voltage check will pass.
Read this codeThrottle/Pedal Position Sensor 'D' Circuit Low Input
One of the two sensors inside the accelerator pedal assembly is reporting near-zero voltage no matter where the pedal is. Different from P0122 — this code is about the pedal side of the drive-by-wire system, not the throttle body.
Read this codeThrottle/Pedal Position Sensor 'D' Circuit High Input
The 'D' accelerator pedal position sensor is reading too high — a signal voltage above its expected window. As the high-input mirror of P2122, it usually traces to a short to voltage, a connector or wiring fault, or a failed pedal sensor. Because drive-by-wire systems treat pedal signals as safety-critical, this often comes with reduced-power limp mode until it's resolved.
Read this codeThrottle/Pedal Position Sensor 'D' Circuit Intermittent
The accelerator pedal's "D" position signal is glitching — momentary dropouts or spikes that make the computer distrust what your foot is asking for.
Read this codeThrottle/Pedal Position Sensor 'E' Circuit
A fault in the accelerator pedal's "E" position sensor circuit — the redundant second signal the computer uses to double-check what the pedal is doing.
Read this codeThrottle/Pedal Position Sensor 'E' Circuit Range/Performance
Pedal sensor E's signal is present but implausible — it disagrees with sensor D or doesn't track pedal movement the way it should.
Read this codeThrottle/Pedal Position Sensor 'E' Circuit Low Input
The 'E' position sensor inside the accelerator pedal assembly — the second of the two redundant sensors — is reporting near-zero voltage no matter where the pedal is. Paired sibling of P2122 but on the redundant sensor circuit.
Read this codeThrottle/Pedal Position Sensor 'E' Circuit High Input
The 'E' accelerator pedal position sensor is reading too high — a signal voltage above its expected window. As the high-input mirror of P2127, and the companion to the 'D'-channel code P2123, it usually traces to a short to voltage, a connector or wiring fault, or a failed pedal sensor. Drive-by-wire systems treat pedal signals as safety-critical, so reduced-power limp mode is common until it's fixed.
Read this codeThrottle/Pedal Position Sensor 'A'/'B' Voltage Correlation
The two throttle position sensors inside the throttle body don't agree with each other. On GM trucks and SUVs in particular this is THE 'Reduced Engine Power' code that strands owners on the shoulder — and the first thing to try is often a $10 can of throttle body cleaner.
Read this codeThrottle/Pedal Position Sensor 'A'/'C' Voltage Correlation
Two of the throttle body's position sensors — A and C — disagree with each other beyond tolerance, so the computer can't trust the throttle's reported position.
Read this codeThrottle/Pedal Position Sensor 'B'/'C' Voltage Correlation
Throttle position sensors B and C disagree beyond tolerance — the redundancy cross-check failed, so the computer limits throttle authority.
Read this codeThrottle/Pedal Position Sensor 'D'/'E' Voltage Correlation
The two sensors inside the accelerator pedal don't agree with each other. Pedal-side mirror of P2135 — same correlation logic, but the failure is in the pedal under the dash, not in the throttle body. No cleaning will fix this one.
Read this codeSystem Too Lean Off Idle (Bank 1)
Bank 1 runs lean once you come off idle and onto part throttle, but not at idle itself and not under real load. A fault confined to that middle band usually belongs to something that changes state as the throttle opens rather than to a leak that is always there.
Read this codeSystem Too Rich Off Idle (Bank 1)
Bank 1 runs rich at part throttle — the operating band where cars actually spend most of their hours. Of all the fuel trim codes, this is the one the owner has usually already noticed, because it shows up as fuel economy falling for no obvious reason.
Read this codeSystem Too Lean Off Idle (Bank 2)
The bank 2 counterpart to P2177 — lean at part throttle on the bank that does not contain cylinder 1. The most useful information on this code is often not in the code itself but in which of its siblings is stored alongside it.
Read this codeSystem Too Rich Off Idle (Bank 2)
Bank 2 is running rich at part throttle. It is easy to file this one under "only one bank, not urgent" — but that reasoning is exactly backwards, because the components a rich condition damages are per-bank, and bank 2's are usually the expensive ones to replace.
Read this codeCooling System Performance
The engine's temperature did not follow the curve the module expected. This is a verdict on a trend rather than a reading, so it sets just as readily for an engine running cold as for one running hot — and the gauge often looks perfectly normal.
Read this codeEngine Coolant Temperature Sensor 2 Circuit
A general fault on the second coolant temperature sensor's circuit. The first job is not to test anything — it is to find out where sensor 2 physically sits on this vehicle, because manufacturers put it in three quite different places and the code means something different in each.
Read this codeEngine Coolant Temperature Sensor 2 Circuit Range/Performance
The second coolant sensor is producing a signal that is electrically perfectly fine and still wrong. This is the only member of the family that fails a comparison rather than a measurement, which means the sensor is frequently innocent and the cooling system is the defendant.
Read this codeEngine Coolant Temperature Sensor 2 Circuit Low
Signal voltage on the second coolant sensor has fallen below what any real temperature could produce. Low volts on a thermistor circuit means low resistance, and low resistance means hot — so the module is being told the engine is far hotter than it is, and may start acting on that.
Read this codeEngine Coolant Temperature Sensor 2 Circuit High
Signal voltage on the second coolant sensor has risen above what any real temperature could produce, which on a thermistor circuit means an open somewhere. This is the failure mode a disconnected plug produces, which is why it turns up so often within days of other work.
Read this codeEngine Coolant Temperature Sensor 2 Circuit Intermittent/Erratic
The second coolant temperature sensor is reporting unstable readings. Because this sensor usually sits in the flow path rather than in the cylinder head, the cause is often coolant behaviour rather than wiring.
Read this codeSystem Too Lean at Idle (Bank 1)
A lean mixture that shows up at idle and disappears once you are moving. The words "at idle" are the useful part: they tell you the leak is a fixed size, because a fixed leak is enormous compared with idle airflow and trivial compared with airflow at speed.
Read this codeSystem Too Rich at Idle (Bank 1)
Too much fuel at idle only. The place to start is the EVAP purge valve, because purge flow is roughly constant while the engine's fuel demand at idle is at its smallest — so the same vapour that is invisible at cruise dominates the mixture at a standstill.
Read this codeSystem Too Lean at Idle (Bank 2)
A lean idle on one cylinder bank only. The fact that it is one bank and not both is the most powerful piece of information in the code, because it eliminates everything the two banks share before you touch a spanner.
Read this codeSystem Too Rich at Idle (Bank 2)
One bank rich, only at idle. That combination clears the fuel system as a whole and points at something that adds a fixed quantity of fuel — which matters most at idle, because idle is when the engine asks for the least.
Read this codeSystem Too Lean at Higher Load (Bank 1)
Bank 1 runs out of fuel correction only when the engine is working hard. The load qualifier is the whole diagnosis: a fault that appears only at load is proportional to flow, which quietly clears the usual suspects.
Read this codeSystem Too Rich at Higher Load (Bank 1)
Bank 1 has too much fuel when the engine is working hard. The module never measures fuel — it calculates it from measured air, so an excess of fuel under load usually means the air measurement is wrong at the top of its range.
Read this codeSystem Too Lean at Higher Load (Bank 2)
One bank goes lean only under load. At idle the two banks share almost everything, but at high load they often do not — which is why this code points at the induction system rather than away from it.
Read this codeSystem Too Rich at Higher Load (Bank 2)
Too much fuel on one bank, only under load. The airflow sensor measures both banks and cannot produce a one-sided error — which leaves that bank's own upstream sensor as the prime suspect, and makes replacing it the right answer more often than usual.
Read this codeO2 Sensor Signal Stuck Lean (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 is reporting a signal that stays biased toward lean and won't switch back and forth the way a healthy sensor should. The car is usually still drivable, but fuel trims and emissions are affected.
Read this codeO2 Sensor Signal Stuck Rich (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 is reporting a signal that stays biased toward rich and won't switch normally. The car usually still drives, but the ECM may be pulling fuel it shouldn't and emissions are affected.
Read this codeO2 Sensor Signal Stuck Lean (Bank 2, Sensor 1)
The upstream oxygen sensor on Bank 2 is reporting a signal that stays biased toward lean and won't switch normally. It's the Bank 2 mirror of P2195. The car usually still drives.
Read this codeO2 Sensor Signal Stuck Rich (Bank 2, Sensor 1)
The upstream oxygen sensor on Bank 2 is reporting a signal that stays biased toward rich and won't switch normally. It's the Bank 2 mirror of P2196. The car usually still drives.
Read this codeIntake Air Temperature Sensor 1/2 Correlation
Two intake air temperature sensors are reporting temperatures that disagree by more than the engine control module allows. Neither sensor has necessarily failed a range check — the problem is that their readings do not correlate, which usually means one has drifted, one is reading a different airstream than expected, or a circuit has added resistance.
Read this codeNOx Sensor Circuit (Bank 1)
A general electrical fault was detected in the NOx sensor circuit on bank 1. The NOx sensor — almost always on diesels — measures nitrogen-oxide levels the emissions system needs to control SCR dosing and monitor the catalyst.
Read this codeNOx Sensor Circuit Range/Performance (Bank 1)
The bank 1 NOx sensor is producing a signal that is electrically valid but out of range or illogical for engine conditions. Often the sensor is aging, contaminated, or drifting rather than fully dead.
Read this codeNOx Sensor Circuit Low (Bank 1)
The module is seeing a below-threshold input from the bank 1 NOx sensor. On most vehicles that sensor is not a simple probe but a small self-testing control unit, so this code very often means the sensor has failed itself rather than that a wire has shorted.
Read this codeNOx Sensor Circuit High (Bank 1)
The bank 1 NOx input has gone above its acceptable limit. The awkward part of this code is that a broken circuit and a genuinely dirty exhaust can produce the same complaint, and the evidence that separates them is usually already sitting in the scan data.
Read this codeNOx Sensor Circuit Intermittent (Bank 1)
The bank 1 NOx signal keeps dropping out and coming back rather than failing outright. That pattern is a strong hint in itself — it points at a connection or a moisture path far more often than at the sensing element.
Read this codeNOx Sensor Heater Control Circuit/Open (Bank 1)
The heater built into the bank 1 NOx sensor is not drawing the current the module expects, and the circuit reads as open. Until the element reaches temperature the sensor cannot measure anything at all — it is blind rather than wrong.
Read this codeNOx Sensor Heater Control Circuit Low (Bank 1)
The control wire for the bank 1 NOx sensor heater is sitting lower than it should. On a ground-switched heater that usually means the circuit is being held on rather than being denied power — an overheating risk, not an underheating one.
Read this codeNOx Sensor Heater Control Circuit High (Bank 1)
The module pulled the bank 1 NOx heater circuit down and the voltage did not follow. On a ground-switched load that reads as high almost always means one thing: no current flowed, because there is nothing on the other end drawing it.
Read this codeNOx Sensor Heater Sense Circuit (Bank 1)
A fault in the feedback path that reports on the bank 1 NOx sensor heater, rather than in the heater itself. This is a circuit whose only job is to watch another circuit, which is why the vehicle often behaves perfectly while it is stored.
Read this codeNOx Sensor Heater Sense Circuit Range/Performance (Bank 1)
The bank 1 NOx sensor heater is working, but not well enough or fast enough to satisfy the module. This is a code about elapsed time rather than about a broken circuit — the classic finding is an element that still heats and simply takes too long.
Read this codeNOx Sensor Heater Sense Circuit Low (Bank 1)
The feedback line that watches the bank 1 NOx sensor heater is reading low. Before condemning anything, find out whether that line is lying or simply reporting a heater that really is off — the other codes stored alongside it answer that in seconds.
Read this codeNOx Sensor Heater Sense Circuit High (Bank 1)
On a monitoring line like this one, high usually means nothing is connected rather than something is shorted to power. That inverts the usual approach — the unplug test is useless here, and a jumper at the sensor connector settles it in one step.
Read this codeNOx Sensor Heater Sense Circuit Intermittent (Bank 1)
The bank 1 heater sense signal is dropping out and returning. Unlike almost every other emissions circuit, this one is routed under the vehicle, so the fault tracks road surface rather than engine temperature — and that changes how you have to test for it.
Read this codeBarometric Pressure Circuit
A general fault in the barometric pressure circuit. Before diagnosing it, find out whether this vehicle even has a barometric sensor as a physical part — on a great many it does not, and that single answer decides the whole repair.
Read this codeBarometric Pressure Circuit Range/Performance
The barometric reading disagrees with the other pressure sensors it should match. Because there is no absolute reference on board, this code is always a comparison — and the sensor it names is often not the one that is wrong.
Read this codeBarometric Pressure Circuit Low
The barometric signal has fallen to the bottom of its electrical range. There is a five-minute unplug test that separates a failed sensor from a shorted wire before you spend anything, and it is worth doing first.
Read this codeBarometric Pressure Circuit High
The barometric signal has climbed to the top of its range. The cause that gets missed is a lost ground — on a pressure sensor that pushes the output up toward the reference with the sensor itself in perfect condition, so test the ground under load before condemning the part.
Read this codeBarometric Pressure Circuit Intermittent/Erratic
Atmospheric pressure is the slowest-moving input on the vehicle, so any movement inside one drive is proof of a fault by itself. That makes this the one code in the family you can confirm from a graph — and the sensor's exposed mounting means the pattern usually follows the weather.
Read this codeO2 Sensor Signal Circuit Shorted to Heater Circuit (Bank 1, Sensor 1)
Battery voltage from the heater is leaking into a signal wire built for a fraction of a volt. This is the upstream sensor, so the corrupted number is actively controlling fuelling — which makes it the one member of this family that can damage the engine while you decide what to do.
Read this codeO2 Sensor Signal Circuit Shorted to Heater Circuit (Bank 1, Sensor 2)
The post-catalyst sensor's signal wire has picked up heater voltage. This position does not control fuelling — it grades the converter — so the expensive mistake here is approving a catalytic converter for a fault that is worth a fraction of it.
Read this codeO2 Sensor Signal Circuit Shorted to Heater Circuit (Bank 1, Sensor 3)
A third sensor on one bank is uncommon, so the first job is confirming this vehicle has one and finding out what it is there for. Where it exists, previous repairs with universal splice-in sensors are a leading cause of this exact fault.
Read this codeO2 Sensor Signal Circuit Shorted to Heater Circuit (Bank 2, Sensor 1)
Heater voltage has reached the signal wire of the sensor that actually controls fuelling on bank 2. Because fuel trim is reported one bank at a time, the giveaway is a lopsided trim reading — one bank at an extreme while the other sits normal.
Read this codeO2 Sensor Signal Circuit Shorted to Heater Circuit (Bank 2, Sensor 2)
A post-converter sensor on the second bank, where the repair is usually simple and the repeat is usually self-inflicted: on a four-sensor vehicle the two downstream sensors are different part numbers, and fitting the wrong one leaves a lead that will short again.
Read this codeO2 Sensor Signal Circuit Shorted to Heater Circuit (Bank 2, Sensor 3)
The rarest member of the family, and the one where the test is cheap but the access is the bill. It also sits on vehicles carrying six oxygen sensors, where a single short can drop the shared heater fuse and produce a code list that looks like six failures.
Read this codeO2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 1)
The first code in the library's wideband oxygen sensor set. A wideband sensor does not send the module a mixture voltage — it lets the module measure its own pumping current, and this code says that current path is broken.
Read this codeO2 Sensor Positive Current Control Circuit Low (Bank 1 Sensor 1)
Pump current below the expected window on the upstream sensor. The cause that catches people out is not a wire at all: many wideband sensors carry an individual calibration resistor inside the connector, so the connector is part of the sensor and cannot be swapped.
Read this codeO2 Sensor Positive Current Control Circuit High (Bank 1 Sensor 1)
Pump current above the expected window. Before suspecting wiring, ask whether the sensor was ever hot enough to work — the pump cell only functions near 750 degrees Celsius, and a cold cell forces the module to push far more current than it should need.
Read this codeO2 Sensor Positive Current Control Circuit/Open (Bank 2 Sensor 1)
The pump current supply to the upstream wideband sensor on bank 2 is open. The single most useful thing about this code is that the engine has a second wideband sensor still working — and that healthy sensor is a better reference than any specification table.
Read this codeO2 Sensor Positive Current Control Circuit Low (Bank 2 Sensor 1)
Current is reaching the bank 2 wideband pump cell, but less of it than the module expects. That distinction matters: a previous repair to this circuit is one of the most common reasons it reads low.
Read this codeO2 Sensor Positive Current Control Circuit High (Bank 2 Sensor 1)
A milliamp circuit is reading higher than it should. Of the three pump current codes this is the one that can destroy hardware, so the order of work is inverted: find the fault before you fit anything new.
Read this codeO2 Sensor Reference Voltage Circuit/Open (Bank 1 Sensor 1)
The regulated reference supply to the upstream sensor on bank 1 is open. The most informative question on this code is not what broke, but what else is quiet — because that reference rail usually feeds several sensors at once.
Read this codeO2 Sensor Reference Voltage Performance (Bank 1 Sensor 1)
The reference supply is present and within legal limits, but not behaving the way a reference is supposed to behave. This is the only judgement-based member of the family, and it is the one a multimeter will happily tell you is fine.
Read this codeO2 Sensor Reference Voltage Circuit Low (Bank 1 Sensor 1)
The reference rail is being dragged below where it should sit. A rail that is pulled down is being loaded by something, and the fastest way to find out what is to start unplugging the things that share it.
Read this codeO2 Sensor Reference Voltage Circuit High (Bank 1 Sensor 1)
A 5-volt reference reading above its window usually means battery voltage has found its way onto it. Treat that as a damage event in progress, not just a fault to look up — everything on that rail is exposed while it lasts.
Read this codeO2 Sensor Reference Voltage Circuit/Open (Bank 2 Sensor 1)
The reference supply to the bank 2 upstream sensor has gone open. Before you touch a wire, find out from the wiring diagram whether the two banks share one reference rail or run on separate ones — that single answer decides how much of the harness is actually suspect.
Read this codeO2 Sensor Reference Voltage Performance (Bank 2 Sensor 1)
A performance code on bank 2 comes with an advantage no single-bank engine ever gets: a second, healthy reference circuit on the same vehicle, in the same weather, on the same drive. Use bank 1 as the control and read the difference, not the number.
Read this codeO2 Sensor Reference Voltage Circuit Low (Bank 2 Sensor 1)
On a transverse V engine, bank 2 is usually the bank against the firewall — longer harness, worse access, and a sensor that can cost several times as much in labour as its bank 1 twin. That economics is what should decide how much diagnostic time you spend here.
Read this codeO2 Sensor Reference Voltage Circuit High (Bank 2 Sensor 1)
Bank 2 harnesses usually cross the engine, and where they cross there is often an intermediate connector bank 1 does not have. Add the extra heat the rear bank lives in and you have the two ingredients for a fault that only exists once the engine is hot.
Read this codeO2 Sensor Negative Current Control Circuit/Open (Bank 1 Sensor 1)
The return side of the pumping circuit is open. On most sensor designs that return is shared with other elements inside the sensor, so a single break here tends to produce a scatter of unrelated-looking codes — and the loudest one is rarely the fault.
Read this codeO2 Sensor Negative Current Control Circuit Low (Bank 1 Sensor 1)
Hunting a short to ground on a circuit whose job is already to be near ground defeats an ohmmeter — it reads low either way. The measurement that actually separates a healthy return from a faulty one is voltage drop while current is flowing.
Read this codeO2 Sensor Negative Current Control Circuit High (Bank 1 Sensor 1)
A return that sits high is a return with resistance in it, and a resistive ground shifts everything measured against it. That is why this code so often arrives dressed as a fuel problem — the mixture numbers are wrong in a consistent direction and the fuel system is innocent.
Read this codeO2 Sensor Negative Current Control Circuit/Open (Bank 2 Sensor 1)
The return conductor for the bank 2 upstream sensor is open. The code names a sensor, not a place — on vehicles where the two banks share a return, the break can be physically nowhere near bank 2.
Read this codeO2 Sensor Negative Current Control Circuit Low (Bank 2 Sensor 1)
The bank 2 return is reading below the window the module expects. That it arrived alone, without a matching bank 1 complaint, is itself a finding — it settles a wiring question that would otherwise cost you a diagram.
Read this codeO2 Sensor Negative Current Control Circuit High (Bank 2 Sensor 1)
The bank 2 return is sitting higher than it should. Before touching a wire, read which way the two banks' fuel trims have diverged — the direction of the split identifies the offending side and rules out the whole class of shared faults.
Read this codeTurbocharger/Supercharger Boost System Performance
The boost system isn't delivering the pressure the PCM expects — a performance fault rather than a single circuit fault. P2263 means measured boost doesn't match the target, which on a turbo engine usually traces to a boost leak, a sticking or failing wastegate or variable-vane mechanism, oil-related turbo problems, or a restriction. Expect reduced power and sluggish acceleration until it's resolved.
Read this codeO2 Sensor Signal Stuck Lean (Bank 1, Sensor 2)
The downstream oxygen sensor on Bank 1 — the one behind the catalytic converter — is reporting a signal stuck toward lean. This is mainly an emissions and catalyst-monitoring code; the car almost always drives normally.
Read this codeO2 Sensor Signal Stuck Rich (Bank 1, Sensor 2)
The post-catalyst sensor on Bank 1 is pinned high and no longer plausible. Before anyone quotes a catalytic converter off the back of it, understand that this exact fault is the most common reason a healthy converter gets condemned.
Read this codeO2 Sensor Signal Stuck Lean (Bank 2, Sensor 2)
The downstream oxygen sensor on Bank 2 — behind the catalytic converter — is reporting a signal stuck toward lean. It's the Bank 2 mirror of P2270 and mainly an emissions code; the car almost always drives normally.
Read this codeO2 Sensor Signal Stuck Rich (Bank 2, Sensor 2)
The post-catalyst sensor on Bank 2 is stuck high. Because this code only exists on two-bank engines, you have something no single-bank vehicle offers — an identical sensor on the other side to check the reading against.
Read this codeNOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)
The downstream NOx sensor (bank 1, sensor 2) is producing an in-range but illogical signal. This sensor, located after the SCR catalyst, verifies how well the system reduced NOx — so a fault can point at the sensor or at real SCR performance.
Read this codeExhaust Gas Recirculation System Performance
The EGR system isn't performing the way the PCM expects — actual exhaust-gas recirculation doesn't match the commanded amount. It's a performance code rather than a single circuit fault, and the overwhelmingly common cause is carbon: clogged EGR passages, a sticking valve, or a fouled cooler. Cleaning or replacing the EGR valve and clearing the passages is the usual fix.
Read this codeDiesel Particulate Filter Pressure Sensor "A" Circuit
A general electrical fault in the circuit that carries the DPF pressure sensor's signal. Unlike the filter-efficiency codes, this one is not a verdict on the filter — it is a complaint about the instrument, and it lives in the worst-located wiring on the vehicle.
Read this codeDiesel Particulate Filter Pressure Sensor "A" Circuit Range/Performance
The pressure signal is electrically fine but does not match what the exhaust is actually doing. This is the one DPF code with a free, decisive, thirty-second test — because with the engine off, the answer has to be zero.
Read this codeDiesel Particulate Filter Pressure Sensor "A" Circuit Low
The signal from the DPF pressure sensor is sitting at the bottom of its range and staying there. Under a vehicle, ground is everywhere — the pipe, the heat shields, the subframe — which is why a chafed wire finds it so easily.
Read this codeDiesel Particulate Filter Pressure Sensor "A" Circuit High
The signal is sitting at the top of its range, which sounds like too much pressure and almost never is. On a pulled-up sensor circuit, high usually means nothing is connected — and the voltage it settles at tells you whether it is an open or something far worse.
Read this codeDiesel Particulate Filter Pressure Sensor "A" Circuit Intermittent/Erratic
The signal is jumping around rather than sitting wrong. Because this sensor reads the exhaust through two small sample hoses rather than touching it directly, the noisy reading is far more often a cracked or blocked hose than a failed sensor.
Read this codeExhaust Gas Recirculation Cooling System Performance
The module has decided the EGR cooler is not removing enough heat from the recirculated exhaust. Before anything else, check the coolant level — this is a heat exchanger with coolant on one side and exhaust on the other, and the failure that matters most is the one that lets them meet.
Read this codeDiesel Particulate Filter Regeneration Duration
A regeneration started and never finished inside the time allowed. On a great many vehicles the reason is not a broken part at all — it is that the journey ended before the burn did, and the failures compound each time it happens.
Read this codeDiesel Particulate Filter Regeneration Frequency
The filter keeps needing to be cleaned sooner than it should. That points upstream at whatever is making more soot than normal — unless the filter has reached the end of its ash life, in which case nothing upstream will help.
Read this codeDiesel Particulate Filter Pressure Sensor "B" Circuit Low
A below-limit input from the second particulate filter pressure sensor. The first job on any "B" code is finding out what B is on your vehicle, because manufacturers use that letter for two completely different sensors in two different places.
Read this codeDiesel Particulate Filter Pressure Sensor "B" Circuit High
An above-limit input from the second particulate filter pressure sensor. This is the one to fix quickly, because a false high reading does not just misinform the module — it makes the module act, and the action it takes puts fuel into your engine oil.
Read this codeDiesel Particulate Filter Pressure Sensor "B" Circuit Intermittent/Erratic
The second particulate filter pressure signal is jumping around rather than reading steadily. On a B circuit the most valuable question is whether the A sensor is misbehaving at the same moment, because a second sensor is almost always wired into the first one's supply and ground.
Read this codeDiesel Particulate Filter Restriction - Soot Accumulation
The filter is holding more soot than it should be. There is usually a window in which this can still be cleared by driving or a forced regeneration, and that window closes — which is why this code is worth acting on the same week rather than the same season.
Read this codeO2 Sensor Circuit Range/Performance (Bank 1, Sensor 1)
The upstream oxygen sensor on Bank 1 is reporting a signal that's out of its expected range or responding too slowly. The check engine light is on, but the car usually still drives normally.
Read this codeO2 Sensor Circuit Range/Performance (Bank 2, Sensor 1)
The upstream oxygen sensor on Bank 2 is reporting a signal that's out of its expected range or responding too slowly. It's the Bank 2 mirror of P2A00. The check engine light is on, but the car usually still drives normally.
Read this codeChassis (C codes)
ABS, traction control, steering, and suspension codes. 60 codes published.
Left Front Wheel Speed Sensor Circuit
The ABS module has lost a trustworthy signal from the left front wheel. Before anything is replaced, find out whether this corner carries an active or a passive sensor — the resistance test that dominates advice on this code is invalid on the type most vehicles now use.
Read this codeLeft Front Wheel Speed Sensor Circuit Range/Performance
The ABS module is getting a left front wheel speed signal but does not believe it — noisy, dropping out, or disagreeing with the other three wheels. Front sensors fail differently from rear ones because their harness is the only one that flexes with steering as well as suspension.
Read this codeRight Front Wheel Speed Sensor Circuit
The right front wheel speed channel has gone dead. What is useful about this corner is that its branch has to cross the engine bay to reach the module, so it passes through junctions the other front wheel does not — and that gives you somewhere to cut the search in half.
Read this codeRight Front Wheel Speed Sensor Circuit Range/Performance
The ABS module is getting a right front wheel speed signal but does not believe it. On left-hand-drive vehicles this is the curb-side corner — the one that meets kerbs, gutter debris and pothole edges — and that changes what you should be looking for.
Read this codeLeft Rear Wheel Speed Sensor Circuit
No usable signal from the left rear wheel. On the rear axle the thing the sensor reads is usually not a toothed steel ring at all but a magnet moulded into the bearing seal — and that changes what can fail and what a new bearing can accidentally break.
Read this codeLeft Rear Wheel Speed Sensor Circuit Range/Performance
The ABS module is getting a left rear wheel speed signal it does not believe. Rear sensors fail for different reasons than front ones — their wiring never sees steering movement, so fatigue is rare and corrosion, contamination and brake-drum debris do most of the damage.
Read this codeRight Rear Wheel Speed Sensor Circuit
The right rear wheel speed channel has gone quiet. The complaint that brings this one in is often not about braking at all — on vehicles with indirect tyre pressure monitoring, losing a wheel speed channel puts a tyre pressure warning on the dash.
Read this codeRight Rear Wheel Speed Sensor Circuit Range/Performance
The ABS module is getting a right rear wheel speed signal it does not believe. This is statistically the cheapest corner to fix — but on many vehicles rear wheel speed also feeds hill-hold, trailer sway control and park assist, so the symptoms can look unrelated to braking.
Read this codeLeft Front ABS Solenoid #1 Circuit Malfunction
The brake module cannot control the isolation valve for the driver's-side front wheel, so it switches off ABS, traction and stability control. Base braking is untouched — but this is one of the two corners that does most of the stopping.
Read this codeLeft Front ABS Solenoid #2 Circuit Malfunction
The outlet valve circuit for the left front brake is not responding as commanded. This is the hardest-worked valve position in the hydraulic unit, and it is the one whose failure costs you steering rather than merely stability.
Read this codeRight Front ABS Solenoid #1 Circuit Malfunction
An isolation valve circuit fault at the passenger-side front wheel. On a left-hand-drive vehicle this is the kerb side, and that changes what you should look for first: impact and corrosion damage rather than gradual electrical wear.
Read this codeRight Front ABS Solenoid #2 Circuit Malfunction
The release valve circuit for the right front brake is not responding as commanded. Ordinary braking is unaffected, but the corner that does the most work in a panic stop has lost its anti-lock protection.
Read this codeLeft Rear ABS Solenoid #1 Circuit Malfunction
An isolation valve fault at the driver's-side rear wheel. Rear valves are not reserved for emergency stops — they work on every firm brake application through electronic brake force distribution, which is why this code often brings a red brake lamp with it.
Read this codeLeft Rear ABS Solenoid #2 Circuit Malfunction
The release valve circuit for the left rear brake failed its electrical check. Base braking is normal, but a surprising number of convenience features stop working alongside anti-lock, because the rear valves do far more than emergency stops.
Read this codeRight Rear ABS Solenoid #1 Circuit Malfunction
An isolation valve fault at the passenger-side rear wheel — the corner furthest from the hydraulic unit. The complaint that brings people in often has nothing to do with braking: hill-hold stops working, or a trailer warning appears.
Read this codeRight Rear ABS Solenoid #2 Circuit Malfunction
The ABS module detected a fault in the right rear ABS solenoid #2 (outlet/dump valve) circuit. ABS, traction, and stability control are disabled, but your normal (base) brakes still work.
Read this codeABS Pump Motor Circuit Malfunction
The ABS module detected a fault in the circuit that drives the anti-lock brake hydraulic pump motor. ABS, traction, and stability control are disabled, but your normal (base) brakes still work.
Read this codeValve Relay Circuit Malfunction
The ABS module detected a fault in the solenoid valve relay circuit that powers the ABS hydraulic valves. ABS, traction, and stability control are disabled, but your normal (base) brakes still work.
Read this codeLow Brake Fluid Circuit Malfunction
The brake or ABS module detected a low brake fluid signal, or a fault in the brake fluid level sensor circuit. It can mean the fluid is genuinely low — often from worn pads or a leak — or an electrical problem in the level-switch circuit.
Read this codeABS/TCS System Pressure Circuit Malfunction
The ABS module detected a fault in the brake pressure sensor circuit it uses for anti-lock and traction control. ABS and traction/stability control are disabled, but your normal (base) brakes still work.
Read this codeLeft TCS Solenoid #1 Circuit Malfunction
A traction control valve on the left channel is not responding electrically. Your ordinary brakes are untouched — what is offline is the system's ability to brake a spinning wheel for you.
Read this codeLeft TCS Solenoid #2 Circuit Malfunction
The second traction valve on the left channel has failed its electrical check. Which other codes arrived alongside it is the most useful clue you have — read the pattern before ordering anything.
Read this codeRight TCS Solenoid #1 Circuit Malfunction
A traction valve on the right channel is not answering electrically. On a left-hand-drive vehicle that is the kerb-side wheel — statistically the one that meets bad surfaces most often in ordinary driving.
Read this codeRight TCS Solenoid #2 Circuit Malfunction
The last of the four traction valve circuits to be reported. If this one arrived with all three of its siblings, stop thinking about valves — a full sweep means something they all depend on has failed.
Read this codeABS/TCS Brake Switch Circuit Malfunction
The ABS/traction control module detected an illogical or missing signal from the brake switch. The brake light switch tells the system when you're braking; a bad signal can disable ABS/traction features and sometimes affect cruise control.
Read this codeElectric Power Steering System Thermal Error
The electric power steering system got too hot and shut its assist off to protect itself. The wheel suddenly feels very heavy, but the car is still steerable and drivable — usually the fault is temporary and clears once the system cools down.
Read this codeLateral Acceleration Sensor Signal
The stability control system detected an implausible or missing signal from the lateral acceleration (side-to-side G) sensor. Stability and traction control may be disabled, but base braking is unaffected.
Read this codeYaw Rate Sensor Circuit
The stability-control system detected a fault in the yaw rate sensor or its signal. Electronic stability control (StabiliTrak/ESC) and traction control are typically disabled, but ABS and your normal brakes still work.
Read this codeABS Enable Relay Contact Circuit Malfunction
The ABS module detected a problem in the ABS enable relay circuit that powers the ABS solenoids/pump. With the relay circuit faulted, the ABS module disables anti-lock braking as a fail-safe while normal (base) braking continues.
Read this codeRear Wheel Speed Sensor Circuit Range/Performance
The ABS module is seeing a missing or out-of-range rear wheel speed signal. ABS, traction control, and stability control are usually disabled, but your normal brakes still work.
Read this codeRear Wheel Speed Signal Erratic
The ABS module is receiving a jumpy, inconsistent rear wheel speed signal. ABS, traction control, and stability control are usually disabled, but your normal brakes still work.
Read this codePowertrain Control Module (PCM) Traction Control Not Allowed
The brake/stability module disabled traction control because the engine computer reported it can no longer manage engine torque. This is a secondary flag — the real problem is a separate engine or sensor fault that must be found first.
Read this codePCM Indicated Traction Control Malfunction
The engine computer told the brake/stability module it cannot perform a requested torque reduction for traction control, usually because of a separate engine fault. Traction and stability control are disabled until the underlying problem is fixed.
Read this codeWheel Speed Sensor Frequency Malfunction
The ABS module detected an illogical or inconsistent wheel speed signal — one wheel's reading disagrees with the others. ABS and traction/stability control may be disabled, but your normal brakes still work.
Read this codeEBCM Relay Circuit Malfunction
The ABS module detected a fault in the electronic brake control module's motor relay circuit. ABS, traction, and stability control are disabled, but your normal (base) brakes still work.
Read this codeEBCM Motor Relay Circuit — High When Off
The ABS control module sees voltage on its pump-motor relay circuit when the relay is commanded off — usually relay contacts stuck closed inside the EBCM.
Read this codePump Motor Circuit Open
The ABS module detected an open (broken) circuit in the anti-lock brake pump motor. ABS, traction, and stability control are disabled, but your normal (base) brakes still work.
Read this codePump Motor Circuit Shorted
The ABS module detected a short in the anti-lock brake pump motor circuit. ABS, traction, and stability control are disabled, but your normal (base) brakes still work.
Read this codeBrake Switch Circuit Malfunction
The ABS module detected an open, shorted, or invalid signal from the brake pedal switch circuit. ABS and traction/stability control may be disabled, but your normal brakes still work. A faulty brake light switch is the most common cause.
Read this codeLongitudinal Acceleration Sensor Circuit
The stability control system detected a fault in the longitudinal (forward/backward) acceleration sensor circuit. On many GM vehicles the number-one cause is a corroded connector rather than a bad sensor. Stability and traction control usually turn off.
Read this codeEBCM Failed to Receive Serial Data From PCM
The ABS module (EBCM) stopped receiving the expected data messages from the engine/powertrain computer (PCM) over the vehicle's communication network. ABS and traction/stability control may be disabled, but base braking still works.
Read this codeRear Propshaft Speed Sensor Circuit
The control module detected a fault in the rear propshaft (driveshaft) speed sensor circuit. On four-wheel-drive and all-wheel-drive vehicles this sensor feeds the transfer case and stability systems, so a fault commonly turns off automatic 4WD/AWD and lights the ABS and Service 4WD warnings.
Read this codeFront Propshaft Speed Sensor Circuit
The control module detected a fault in the front propshaft (driveshaft) speed sensor circuit. On automatic four-wheel-drive and all-wheel-drive vehicles this signal tells the transfer case how fast the front driveline is turning, so a fault commonly disables automatic 4WD/AWD and lights the ABS and Service 4WD warnings.
Read this codeTransfer Case Encoder Motor ‘A’ or ‘B’ Circuit Malfunction
The Transfer Case Control Module detected an electrical fault in the encoder motor 'A' or 'B' control circuit — the small motor that shifts an electronic four-wheel-drive transfer case between modes. When it sets, shifting is disabled and the Service 4WD light stays on.
Read this codeTransfer Case Encoder Circuit Malfunction
The Transfer Case Control Module received an illogical or out-of-range signal from the transfer case encoder — the sensor that reports which range the transfer case is actually in. It is one of the most common 4WD codes on GM trucks, and bad grounds are behind a large share of cases.
Read this codeTransfer Case System Malfunction (Unable to Correct Wheel Slip)
The transfer case shift control module tried to send torque to the front wheels but could not reduce the speed difference between the front and rear driveshafts within about 10 seconds. Automatic 4WD is disabled and the Service 4WD light comes on.
Read this codeFront Axle Actuator (Switch) Control Circuit
The Transfer Case Control Module commanded the front axle to engage or disengage but did not get the expected confirmation from the front axle actuator's position switch. To protect the driveline the module disables 4WD and turns on the Service 4WD light.
Read this codeTransfer Case Unable to Complete Shift
The electronic transfer case tried to shift into the requested mode or range and could not finish the shift. The system usually reverts to its previous mode, flashes the requested-mode light, and turns on the Service 4WD indicator.
Read this codeTransfer Case Range Position Sensor Circuit
The Transfer Case Control Module detected a fault in the transfer case range/position sensor circuit — the sensor that reports which drive mode the transfer case is in. On many GM trucks it is often a connector pin-tension problem rather than a failed sensor.
Read this codeSteering Wheel Position Sensor Circuit
The stability-control system detected a fault in the steering wheel position (angle) sensor circuit. Stability control and traction control are usually disabled and a 'Service StabiliTrak' or ESC message often appears, but the car still steers and brakes normally.
Read this codeSteering Position Sensor Circuit (Invalid Data)
A module received invalid or implausible data from the steering position (steering angle) sensor. Stability control and traction control usually turn off, and on some vehicles power steering behavior is affected.
Read this codeElectric Power Steering Motor Circuit Malfunction
The power steering control module detected an electrical fault — an open or short — in the electric steering assist motor circuit. Steering assist is usually reduced or lost, making the wheel heavy, though the car remains steerable.
Read this codeElectric Steering Motor Circuit Range/Performance
The electric power steering motor is connected and running, but it is drawing incorrect current or not performing as expected — often a sign of a mechanical bind. The wheel may feel heavy, uneven, or inconsistent to turn.
Read this codeSteering Wheel Torque Sensor Circuit
The power steering control module detected a fault in the steering torque (effort) sensor circuit. This sensor tells the system how hard you are turning the wheel, so a fault usually reduces or disables power assist.
Read this codeElectronic Control Unit (EBCM) Internal Malfunction
The control module — most often the electronic brake control module (EBCM) — reported an internal fault such as a memory, checksum, or self-test failure. ABS, traction, and stability control are usually disabled, but your normal brakes still work.
Read this codeSystem Disabled Information Stored
The stability/ABS module disabled its functions and stored an informational note that another fault or invalid data is present. On its own it usually points you to look elsewhere — the real problem is whatever caused the system to shut itself off. Normal braking still works.
Read this codeSteering Position Signal Malfunction
The stability-control system received an invalid or implausible steering position signal. Stability and traction control are usually disabled and a 'Service StabiliTrak' or ESC message often appears, but the car still steers and brakes normally.
Read this codeControl Module Power Circuit / Device Power Fault
A control module (often the ABS or another chassis module) saw its supply voltage drop too low or spike too high. The vast majority of C0800 cases are a weak battery, corroded terminals, or a high-resistance ground/cable — not the module itself.
Read this codeDevice Voltage Low
A chassis module — most often the ABS/EBCM — saw its supply voltage drop too low to operate safely. The vast majority of C0899 cases are a weak battery, corroded terminals, or a charging fault, not the module itself.
Read this codeControl Module Power Circuit Malfunction
The ABS module (EBCM) detected a supply-voltage problem — most often voltage too high — on its power circuit and shut its functions down to protect itself. ABS and traction/stability control are disabled, but base braking still works.
Read this codeBody (B codes)
Airbag/SRS, HVAC, lighting, and cabin electronics codes. 73 codes published.
Driver Frontal Stage 1 Deployment Control (Subfault)
The restraints module cannot verify the first-stage firing loop for the driver's airbag. Two things make this the most consequential deployment code on the vehicle: stage 1 is the stage that fires in almost every crash, and the driver's loop is the only one that runs through a part which moves every time you steer.
Read this codeDriver Frontal Stage 2 Deployment Control (Subfault)
The airbag/SRS control module detected an electrical fault in the second-stage firing loop for the driver's frontal airbag. The driver airbag may not deploy at full force as designed, so this needs prompt professional attention.
Read this codePassenger Frontal Stage 1 Deployment Control (Subfault)
An electrical fault in the first-stage firing loop of the passenger frontal airbag. Stage 1 is the stage that fires in essentially every frontal deployment, which makes this the most consequential loop fault in the passenger-side family — and on a recently repaired car it is also the one that most often means the airbag is not there.
Read this codePassenger Frontal Stage 2 Deployment Control (Subfault)
The restraints module cannot verify the second-stage firing circuit for the passenger's airbag. The passenger side is the only one with a legitimate reason to switch itself off, so the first job here is separating a genuine circuit fault from a system that is behaving exactly as designed.
Read this codePassenger Frontal Stage 3 Deployment Control (Subfault)
The airbag/SRS control module detected an electrical fault in the passenger frontal airbag's third-stage deployment loop. The passenger airbag may not fire as designed, so this needs prompt professional attention.
Read this codePassenger Knee Bolster Deployment Control (Subfault)
An electrical fault in the passenger knee airbag firing loop. Its connector lives behind the lower dash panel next to the fuse box, which makes it the SRS circuit most often disturbed by work that had nothing to do with the airbag system at all.
Read this codeLeft Side Airbag Deployment Control (Subfault)
The airbag/SRS control module detected an electrical fault in the left-side airbag deployment loop. Side-impact protection on that side may not deploy as designed, so this needs prompt professional attention.
Read this codeLeft Curtain Deployment Control 1 (Subfault)
The restraints module cannot verify the left curtain airbag's first firing loop. Before assuming a crash or a failed bag, ask a different question: has the windscreen been out, or the headliner been down? That circuit runs behind trim panels that come off for reasons having nothing to do with airbags.
Read this codeLeft Curtain Deployment Control 2 (Subfault)
A fault on the left curtain's second firing loop. The first question is not what broke but whether that second loop exists on this vehicle at all — a module carrying the wrong build configuration reports a circuit that was never installed, and it reports it as an open, which reads exactly like a broken wire.
Read this codeRight Side Airbag Deployment Control (Subfault)
The airbag/SRS control module detected an electrical fault in the right-side airbag deployment loop. The right seat-mounted side airbag may not deploy as designed, so this needs prompt professional attention.
Read this codeRight Curtain Deployment Control 1 (Subfault)
An electrical fault in the primary firing circuit for the right roof-rail curtain airbag. This is the loop every curtain-equipped vehicle has, and its connector sits at the A-pillar — which is why windscreen replacement is the single most common non-collision cause.
Read this codeRight Curtain Deployment Control 2 (Subfault)
A fault in the second firing circuit for the right curtain airbag. The first question is architectural rather than electrical — this code can only be genuine on a vehicle whose curtain is fired through two channels, and the second channel usually lives at the rear of the roof rail, not the front.
Read this codeSecond Row Left Side Airbag Deployment Control (Subfault)
A firing-loop fault on the second-row left side airbag. A side bag has almost no time to work, which is why it is single-stage — and why the seat it lives in is the thing most likely to have broken its circuit.
Read this codeSecond Row Left Frontal Stage 1 Deployment Control (Subfault)
An electrical fault in the first-stage firing loop of the second-row left frontal airbag — the stage that fires in essentially every qualifying crash, which is what makes this fault the more consequential of the pair.
Read this codeSecond Row Left Frontal Stage 2 Deployment Control (Subfault)
An electrical fault in the second-stage firing loop of the second-row left frontal airbag — a circuit that is invisible in normal use and even in a moderate crash, because the only thing that ever exercises it is the module's own self-test.
Read this codeSecond Row Left Frontal Stage 3 Deployment Control (Subfault)
The restraints module found the firing circuit for the third and final stage of a second-row left frontal airbag out of specification. That stage only fires in the most severe crashes — which shapes both how urgent this is and what it means for anyone working on the vehicle.
Read this codeSecond Row Right Side Airbag Deployment Control (Subfault)
The restraints module found the firing circuit for the right-hand second-row side airbag out of specification. Unlike a frontal airbag, this one almost always lives inside the seat itself — which is where the fault usually lives too.
Read this codeSecond Row Right Frontal Stage 1 Deployment Control (Subfault)
The restraints module found the first-stage firing circuit for a second-row right frontal airbag out of specification. Stage 1 is the charge that fires in nearly every deployment, which makes this the most consequential fault of the staged set.
Read this codeSecond Row Right Frontal Stage 2 Deployment Control (Subfault)
The second firing stage of the second-row right frontal airbag is out of specification. The bag can still deploy — but only ever at the force reserved for a mild crash, which is why this fault gets deferred and why deferring it is expensive.
Read this codeSecond Row Right Frontal Stage 3 Deployment Control (Subfault)
The restraints module cannot verify the third-stage firing loop of the second-row right frontal airbag. Before chasing wiring, establish whether this vehicle was actually built with a three-stage inflator at that position — many were not.
Read this codeThird Row Left Side Airbag Deployment Control (Subfault)
A fault in the firing loop of a torso airbag built into the left third-row seat. Because this bag lives inside the seat rather than the body structure, its wiring is the only airbag circuit in the vehicle that has to survive being folded flat every time someone needs the cargo space.
Read this codeThird Row Left Frontal Stage 1 Deployment Control (Subfault)
The generic definition names a third-row frontal airbag — a device almost no production vehicle actually has. Before testing anything, the useful move on this code is to look it up in your manufacturer's own table, because the odds are good that the generic text is not what your module means.
Read this codeThird Row Left Frontal Stage 2 Deployment Control (Subfault)
A firing-loop fault at the third-row left position. This loop is the longest restraints circuit in the vehicle and it terminates under a load floor, which is why water and cargo damage account for so many of these.
Read this codeThird Row Left Frontal Stage 3 Deployment Control (Subfault)
The restraints module found a third-row left frontal airbag firing circuit out of specification. What makes this different from the same fault further forward is distance: this loop is at the end of the longest restraints wiring run in the vehicle.
Read this codeThird Row Right Side Airbag Deployment Control (Subfault)
The mirror of the left-side code, on the corner of the vehicle that gets used the most. Whether this code appears alone or alongside its left-hand twin is the single most useful piece of triage available, and it decides whether you open a seat or go looking upstream.
Read this codeThird Row Right Frontal Stage 1 Deployment Control (Subfault)
One of three codes covering the same right-hand third-row position, which makes counting them the fastest diagnosis available — and on a vehicle with a rebuilt or salvage history, the count usually points somewhere other than a new fault.
Read this codeThird Row Right Frontal Stage 2 Deployment Control (Subfault)
A deployment loop assigned to the third row right position has failed its electrical check. Third row restraint circuits are the longest and worst-routed wiring in the vehicle — they cross the rear wheel well area and pass under seats that fold — which is why corrosion and crushing dominate here in a way they never do at the front.
Read this codeThird Row Right Frontal Stage 3 Deployment Control (Subfault)
A fault on the third stage of a multi-stage deployment device. The single most informative thing about this code is what else is stored alongside it: all stages of one device share a connector and a harness branch, so one stage faulting alone means the squib, and every stage faulting together means the wiring.
Read this codeDriver Seatbelt Sensor (Subfault)
The airbag/SRS control module detected a fault in the driver's seat belt sensor circuit — the sensor that tells the restraint system whether the driver is buckled. Airbag and pretensioner behavior may be affected, so this needs prompt professional attention.
Read this codeFirst Row Center Seatbelt Sensor (Subfault)
A restraints module fault on the middle front seating position's belt sensor. Before testing anything, establish that the vehicle actually has that seat — this is the one belt code that a correctly working car can store because the module was configured for a different trim level.
Read this codePassenger Seatbelt Sensor (Subfault)
A restraints module fault on the front passenger belt buckle. Unlike the other belt sensors, this one is an input to airbag deployment strategy rather than just the reminder chime — which is why a fault here can change what the passenger airbag does in a crash.
Read this codeDriver Seatbelt Tension Sensor (Subfault)
The restraints module has flagged the driver belt tension sensor circuit. On the driver side this is a belt-use and reminder input rather than an airbag suppression input, which changes both the urgency and the likely cause.
Read this codePassenger Seatbelt Tension Sensor (Subfault)
The restraints module has flagged the passenger belt tension circuit. This is the seat where tension feeds airbag suppression decisions, so a bad reading here has a consequence the vehicle actually acts on.
Read this codeDriver Seatbelt Pretensioner "A" Deployment Control (Subfault)
The restraints module cannot verify the driver's belt pretensioner firing circuit. What sets this position apart is movement: the driver's seat is adjusted more than any other in the vehicle, so the wiring under it has flexed more times than any other restraint circuit on board.
Read this codeFirst Row Center Seatbelt Pretensioner Deployment Control (Subfault)
The restraints module cannot verify the firing circuit for the middle front seat belt pretensioner. This position only exists on bench-seat and three-across vehicles, which makes a seat that has been swapped or converted one of the more likely explanations before any hardware is suspected.
Read this codePassenger Seatbelt Pretensioner "A" Deployment Control (Subfault)
The restraints module has rejected the firing circuit for the front passenger pretensioner. The passenger seat carries more wiring than any other seat in the vehicle, so this code very often arrives with company — and the shared loom is usually the real fault.
Read this codePassenger Seatbelt Pretensioner "B" Deployment Control (Subfault)
The airbag/SRS control module detected a fault in the passenger seat belt pretensioner 'B' deployment circuit — a second pyrotechnic device that tightens the passenger's belt in a crash. The pretensioner may not fire when needed, so this needs prompt professional attention.
Read this codeFirst Row Center Seat Belt Load Limiter Deployment Control (Subfault)
The airbag/SRS control module detected a fault in a front-row restraint deployment circuit. Part of the supplemental restraint system may not work as designed, so this needs prompt professional attention.
Read this codeLeft Frontal Restraints Sensor (Subfault)
A forward crash sensor exists for one reason: to see the impact before the module in the middle of the car can. Losing this one does not switch the airbags off — it takes away the early warning and leaves the deployment decision to be made later, from further back.
Read this codeLeft Side Restraints Sensor 1 (Subfault)
The restraints module has a fault on the first-indexed left-side impact sensor circuit. The number is an index in a wiring diagram rather than a place on the car — establishing which physical satellite it points at is the whole first half of this job.
Read this codeLeft Side Restraints Sensor 2 (Subfault)
A restraints module fault on the second-indexed left-side sensor circuit. This is the index where manufacturers diverge most — on some vehicles it is a side impact satellite, on others it belongs to occupant sensing entirely.
Read this codeLeft Side Restraints Sensor 3 (Subfault)
A restraints fault at the third left-side sensor index — the one most likely to describe hardware the vehicle was never built with. Settle the configuration question before spending anything on parts.
Read this codeCenter Frontal Restraints Sensor (Subfault)
The centre sensor is not a spare for the outer two. Its job is classification — comparing when the middle of the car felt the impact against when the corners did is how the module tells a square head-on from an offset one, and that changes what fires and how hard.
Read this codeRight Frontal Restraints Sensor (Subfault)
On a left-hand-drive vehicle this is the kerb-side corner, and kerbs, gutters and wheel-arch debris are what it lives with. It also sits in a decision chain the other frontal sensor does not — the one that decides whether the passenger airbag should fire at all.
Read this codeRight Side Restraints Sensor 1 (Subfault)
A restraints fault at the first right-side sensor index. On left-hand-drive vehicles this is the kerb side, which exposes it to impacts and standing water the driver's side never sees — and it sits alongside the occupant sensing hardware under the passenger seat.
Read this codeRight Side Restraints Sensor 2 (Subfault)
The airbag/SRS control module detected a fault in the right side restraints (impact) sensor 2 circuit. Side airbag timing on that side may be affected, so this needs prompt professional attention.
Read this codeRight Side Restraints Sensor 3 (Subfault)
A frontal crash gives the module several feet of engine bay to read and tens of milliseconds to think. A side impact gives it a few inches of door and single-digit milliseconds — which is why side sensors are bolted out at the impact surface, and why door work is what disturbs them.
Read this codeRoll Over Sensor (Subfault)
The airbag/SRS control module detected a fault with the roll over sensor. Rollover-triggered protection such as curtain airbags and pretensioners may be affected, so this needs prompt professional attention.
Read this codeLeft Side Restraints Sensor 4 (Subfault)
The restraints module has a fault with what it calls left side sensor 4. Before anything else, note the number: most vehicles do not have four side sensors on one side, and confirming that this one does is the step that decides whether you are chasing a component or a configuration.
Read this codeLeft Side Restraints Sensor 5 (Subfault)
A left flank restraints sensor is not reporting acceptably. The question that decides this whole diagnosis is what kind of sensor it is, because two completely different technologies are used in these positions and one of them fails for reasons that have nothing to do with electronics.
Read this codeLeft Side Restraints Sensor 6 (Subfault)
The airbag module has a fault with left-side impact sensor 6. The word Subfault in the title is the important part — the base code tells you almost nothing, and the symptom byte stored with it tells you almost everything.
Read this codeRight Side Restraints Sensor 4 (Subfault)
A restraints sensor on the right flank is not reporting acceptably. On a left-hand-drive vehicle the right side is the kerb side, and that single geographic fact predicts most of what goes wrong here far better than any general theory about sensor failure.
Read this codeRight Side Restraints Sensor 5 (Subfault)
A right flank restraints sensor has stopped reporting acceptably. If it is not the only sensor code stored, stop treating them as separate problems — on a modern restraints system the set of codes that arrived together is a map of the wiring, and it will point at the break.
Read this codeRight Side Restraints Sensor 6 (Subfault)
A fault on right-side impact sensor 6. Whether this code arrived on its own or with satellite faults from elsewhere in the car decides the whole diagnosis, because on many systems all the satellites hang off one shared link and a single break silences several at once.
Read this codeOccupant Classification System (Subfault)
The airbag/SRS control module detected a fault in the Occupant Classification System, which decides whether the front passenger airbag should be enabled. Passenger airbag operation may be affected, so this needs prompt professional attention.
Read this codeOccupant Position System (Subfault)
The restraints module has a problem with the system that works out where the front occupant is sitting. Position is not the same question as classification, and on many designs the sensing is done without touching anyone — which means the first place to look is the cabin, not the wiring.
Read this codeDriver Seat Occupant Classification Sensor A (Subfault)
The airbag/SRS control module detected a fault with the driver-seat occupant classification sensor A, part of the system that senses the driver's seat occupancy for restraint decisions. Airbag operation may be affected, so this needs prompt professional attention.
Read this codeDriver Seat Occupant Classification Sensor B (Subfault)
The airbag/SRS control module detected a fault with the driver-seat occupant classification sensor B, part of the system that senses the driver's seat occupancy for restraint decisions. Airbag operation may be affected, so this needs prompt professional attention.
Read this codeDriver Seat Track Position Restraints Sensor (Subfault)
The airbag/SRS control module detected a fault with the driver seat track position sensor — the sensor that tells the restraint system how far forward or back the driver's seat is set. Airbag deployment strategy may be affected, so this needs prompt professional attention.
Read this codeDriver Seat Recline Position Restraints Sensor (Subfault)
The airbag/SRS control module detected a fault with the driver seat recline (seatback angle) position sensor, used by the restraint system to tailor airbag behavior to how far the seatback is reclined. Airbag operation may be affected, so this needs prompt professional attention.
Read this codeDriver Seat Occupant Position Sensor "D" (Subfault)
The airbag/SRS control module detected a fault with driver-seat occupant position sensor D — one of the sensors that judge where the driver is positioned for restraint decisions. Airbag operation may be affected, so this needs prompt professional attention.
Read this codeDriver Seat Occupant Position Sensor "E" (Subfault)
The airbag/SRS control module detected a fault with driver seat occupant position sensor E, one of the sensors that judge where the driver's body is positioned so the restraint system can tailor airbag deployment. This needs prompt professional attention.
Read this codePassenger Seat Occupant Classification Sensor A (Subfault)
The airbag/SRS control module detected a fault with the passenger-seat occupant classification sensor A — part of the system that senses who is in the passenger seat to decide how the passenger airbag should deploy. This needs prompt professional attention.
Read this codePassenger Seat Occupant Classification Sensor B (Subfault)
The airbag/SRS control module detected a fault with the passenger-seat occupant classification sensor B — a second sensor in the system that senses who is in the passenger seat to decide how the passenger airbag should deploy. This needs prompt professional attention.
Read this codeSensor Cleaning Air Blower Actuator A
The SAE-generic definition is a fault in a sensor-cleaning air blower actuator, but many GM vehicles use B0100 for the Electronic Front End (frontal impact) airbag sensor instead. Confirm which system your make means before deciding how urgent it is.
Read this codeFewer Than the Required Number of Keys Programmed (PATS)
Ford's Passive Anti-Theft System has fewer keys programmed than it requires — usually fewer than two. The car typically still starts with a working key; the fix is to program an additional key.
Read this codeAir Temperature Internal Sensor Circuit Failure
The climate control module detected a fault in the in-cabin (interior) air temperature sensor circuit. The automatic climate control may not regulate temperature correctly, but the vehicle drives normally.
Read this codeBattery Voltage Low
A control module detected that system (battery) voltage dropped below its acceptable threshold. It usually points to the battery, charging system, or their connections rather than the module reporting it.
Read this codeECU Is Defective
A control module has run its internal self-test and reported that it is defective. It usually points to an internal module fault, but low or unstable system voltage can trigger it too, so verify the power supply first.
Read this codePATS Ignition Key Transponder Signal Is Not Received
Ford's Passive Anti-Theft System did not receive a valid signal from the ignition key's transponder chip. The engine may crank but not start because the anti-theft system has disabled it.
Read this codePATS Received Incorrect Key-Code From Ignition Key Transponder
Ford's Passive Anti-Theft System read a key, but the key isn't programmed into this vehicle's memory. The engine cranks but won't start until the key is programmed or a recognized key is used.
Read this codePATS Received Invalid Format Of Key-Code From Ignition Key Transponder
Ford's Passive Anti-Theft System read only a partial or garbled code from the key transponder. It usually points to interference at the ignition or a marginal/unapproved key rather than a dead key.
Read this codeAntenna Not Connected (PATS Transceiver)
Ford's Passive Anti-Theft System detected that the transceiver antenna around the ignition is failed or disconnected. Because it can't read any key, the engine cranks but won't start.
Read this codeNetwork & communication (U codes)
Module-to-module communication and software compatibility codes. 281 codes published.
High Speed CAN Communication Bus
A general fault on the vehicle's high-speed CAN communication bus — the backbone network that lets modules talk to each other. Usually a wiring, connector, or single-module fault that disrupts the whole network.
Read this codeHigh Speed CAN Communication Bus (Performance)
The powertrain backbone is still passing traffic, but the signal quality on it has degraded. This bus has a defined electrical specification you can actually measure against — 60 ohms across a terminated pair, a differential waveform with known voltages — which makes it the one network fault a scope can settle.
Read this codeHigh Speed CAN Communication Bus (+) Open
A break in the CAN-High conductor. An open does not kill the network the way a short does — it cuts it in half, and each half carries on talking to itself while reporting that the other half has vanished.
Read this codeHigh Speed CAN Communication Bus (+) Low
CAN-High is being held down when it should be driven up. That inverts the differential into a state no receiver has a definition for, and transmitting modules detect it themselves within microseconds and take themselves off the network.
Read this codeHigh Speed CAN Communication Bus (+) High
CAN-High is pinned above its normal range, which drives the bus differential permanently to the dominant state. That is not a degraded network — it is a jammed one, and the practical consequence is that no module can transmit, including the one you are trying to read the code from.
Read this codeHigh Speed CAN Communication Bus (-) Open
A break in the CAN-Low conductor. The reason CAN uses two twisted wires is noise cancellation, and losing one destroys it — so this fault often behaves erratically under electrical load rather than failing cleanly.
Read this codeHigh Speed CAN Communication Bus (-) Low
CAN-Low pulled below where it should rest. Unlike a short to battery voltage, a short to ground does not damage anything — which makes this the one bus fault that stays put long enough to be found by halving the network.
Read this codeHigh Speed CAN Communication Bus (-) High
CAN-Low has been pulled up toward CAN-High, collapsing the difference between them. The network does not jam — it goes quiet, and modules fall off one at a time as their error counters run out, which is why this fault so often arrives as a rolling, intermittent complaint.
Read this codeHigh Speed CAN Communication Bus (-) Shorted to Bus (+)
The two high-speed CAN wires — CAN-Low and CAN-High — are shorted together. This collapses the bus voltage and disrupts communication for nearly every module on the network. Usually a wiring or connector fault.
Read this codeMedium Speed CAN Communication Bus
A general fault on the vehicle's medium-speed CAN bus — the slower network that typically links body, comfort, and convenience modules. Usually a wiring, connector, or single-module fault on that bus.
Read this codeMedium Speed CAN Communication Bus (Performance)
The medium-speed CAN bus is communicating, but not reliably — messages are corrupted, intermittent, or out of spec. A 'performance' fault points to a degrading network rather than a fully dead one.
Read this codeMedium Speed CAN Communication Bus (+) Open
A break in the CAN-High conductor of the medium-speed network. Which modules can still be reached tells you where the break is, and a single resistance reading at the diagnostic connector confirms it before any trim comes off.
Read this codeMedium Speed CAN Communication Bus (+) Low
The CAN-High wire is being held down when it needs to be free to swing up. Because almost every metal surface a harness can rub against is already at ground potential, this is the physical-damage code of the medium-speed bus family.
Read this codeMedium Speed CAN Communication Bus (+) High
Battery-level voltage has found its way onto a five-volt logic network. This is the one bus fault that destroys hardware rather than merely interrupting it, so expect the repair to include modules that were fine before the short happened.
Read this codeMedium Speed CAN Communication Bus (-) Open
A break in the CAN-Low conductor of the medium-speed network. Because this wire sits nearest ground potential, poor module grounding imitates it convincingly, and grounds are the cheapest thing to rule out first.
Read this codeMedium Speed CAN Communication Bus (-) Low
CAN-Low pinned down looks to the network exactly like a message that never stops. Every node treats it as a permanently busy bus, error counters climb, and the network shuts itself off — which is why this fault produces a completely dead bus rather than a flaky one.
Read this codeMedium Speed CAN Communication Bus (-) High
CAN-Low sitting too high does not kill the network — it narrows the margin the receivers depend on. This is the intermittent one: features that work in the morning and drop out in the afternoon, and a fault that refuses to appear on the workshop floor.
Read this codeMedium Speed CAN Communication Bus (-) shorted to Bus (+)
The negative (CAN-Low) wire of the medium-speed bus is shorted to the positive (CAN-High) wire. With the two lines tied together the voltage difference collapses and modules on that bus can no longer communicate.
Read this codeLow Speed CAN Communication Bus
A general fault on the vehicle's low-speed CAN bus — the slowest network, used for low-priority comfort and convenience features. Usually a wiring, connector, or single-module fault on that bus.
Read this codeVehicle Communication Bus B
An unqualified fault on the second vehicle bus — no error state named, no module named. The most informative thing available is not a meter reading but the list of which modules still answer.
Read this codeVehicle Communication Bus B (Performance)
"Bus B" is a label, not a technology. Until you look up what the manufacturer assigned to that letter on this specific vehicle, you do not know its speed, its wiring, whether it is even terminated — and every test you might run could be the wrong one.
Read this codeControl Module Communication Bus A Off
A control module has counted so many communication errors that it shut itself off the CAN bus to protect the network — the 'bus off' state. Almost always a wiring short or a failed module transceiver.
Read this codeControl Module Communication Bus B Off
A control module counted so many communication errors on the second bus (Bus B) that it shut itself off the network — the 'bus off' state. Almost always a wiring short or a failed module transceiver on that bus.
Read this codeControl Module Communication Bus C Off
"Bus off" is not a description, it is a defined hardware state. A CAN controller counts its own transmit failures and takes itself off the network when the count passes 255 — which means the module reporting this is often the victim rather than the culprit.
Read this codeLost Communication with ECM/PCM
Another module on the vehicle's communication network has lost contact with the engine control module. Almost always a wiring, power, or ground issue — and frequently a no-start condition.
Read this codeLost Communication with TCM (Transmission Control Module)
A module on the network can no longer hear from the transmission control module. Often a power, ground, or wiring fault at the TCM — and frequently the transmission drops into limp mode.
Read this codeLost Communication with Transfer Case Control Module
A module on the network can no longer hear from the transfer case control module. Usually a power, ground, or wiring fault — and because this module manages four-wheel and all-wheel drive, the vehicle may lose 4WD/AWD function or default to a single drive mode.
Read this codeLost Communication with Gear Shift Module
A module on the network can no longer hear from the gear shift module — the shift-by-wire gear selector controller. Often a power, ground, or wiring fault, and on shift-by-wire vehicles the transmission may refuse to change gears or default to a fail-safe.
Read this codeLost Communication with Cruise Control Module
A module on the network can no longer hear from the cruise control module. Usually a power, ground, or wiring fault — and on vehicles with adaptive cruise control, the radar-based following and speed features go offline along with conventional cruise.
Read this codeLost Communication with Fuel Injector Control Module
The network has lost the module that actually drives the injectors. This module is unlike any other node on the bus because it handles serious voltage and current of its own — which is why a communication code here points at the module's power supply far more often than at the network.
Read this codeLost Communication with Glow Plug Control Module
A module on the network can no longer hear from the glow plug control module. Usually a power, ground, or wiring fault — and because this diesel module preheats the cylinders, you may get hard cold starts, rough cold running, and white startup smoke.
Read this codeLost Communication with Throttle Actuator Control Module
A module on the network can no longer hear from the throttle actuator control module. Usually a power, ground, or wiring fault — and because this module runs the electronic throttle, the engine often drops into reduced-power limp mode or won't respond to the pedal.
Read this codeLost Communication With Alternative Fuel Control Module
A module has stopped receiving messages from the alternative fuel control module over the data network. This module manages CNG, LPG, or bi-fuel operation, so a comms loss can affect running on the alternative fuel.
Read this codeLost Communication with Fuel Pump Control Module
The network has lost the module that varies fuel pump speed. Its defining feature is location — it is mounted at the back of the vehicle near the tank, in the road-spray and salt zone, which makes a corroded connector the most likely cause by a wide margin.
Read this codeLost Communication with Drive Motor Control Module
A module on the network can no longer hear from the drive motor control module. Usually a power, ground, or wiring fault — and because this module runs the electric traction motor, a hybrid or EV may lose propulsion, cut power, or refuse to move.
Read this codeLost Communication with Battery Energy Control Module A
The module that decides whether the high-voltage pack may be connected has gone quiet, so the pack stays disconnected. The dead car is the design working as intended — and it sets off a 12-volt drain that will wreck your diagnosis if you do not stop it first.
Read this codeLost Communication with Battery Energy Control Module B
Before chasing a wire, establish that a second battery controller exists on this vehicle at all — plenty do not, and on those the code is a configuration error. Where B does exist it is a monitoring unit rather than the contactor authority, so the car usually still moves, just worse.
Read this codeLost Communication with Emissions Critical Control Information
A module on the network stopped receiving the emissions-critical data it expects from another controller. Usually a wiring, power, or ground fault on the bus, it can disable emissions monitors, trip the check engine light, and cause a failed inspection.
Read this codeLost Communication with Four-Wheel Drive Clutch Control Module
A module on the network can no longer hear from the four-wheel drive clutch control module. Often a power, ground, or wiring fault — and the AWD/4WD system typically defaults to two-wheel drive with a warning light on.
Read this codeLost Communication with ECM/PCM B
A module on the network can no longer hear from the second engine/powertrain control module (ECM/PCM B). Usually a power, ground, or wiring fault — and because this module helps run the powertrain, the engine may run poorly, lose power, or fail to start.
Read this codeLost Communication with ABS Control Module
A module on the network can no longer hear from the ABS (anti-lock brake) control module. Anti-lock braking, traction control, and stability control are typically disabled — usually a power, ground, or wiring fault at the ABS unit.
Read this codeLost Communication with Vehicle Dynamics Control Module
A module on the network can no longer hear from the vehicle dynamics control module, which runs stability and traction control. Usually a power, ground, or wiring fault, it typically disables ESC/traction control and lights the stability and ABS warnings.
Read this codeLost Communication with Yaw Rate Sensor Module
The stability controller has stopped hearing from the yaw rate sensor. That sensor is the only device on the vehicle that can tell whether the car is rotating, and nothing else can substitute for it — which is why losing it shuts stability control down completely rather than degrading it.
Read this codeLost Communication with Lateral Acceleration Sensor Module
The lateral acceleration message has stopped arriving. This sensor measures sideways g-force with an accelerometer, and because an accelerometer cannot tell cornering force apart from gravity, it behaves in a way that surprises people the first time they test one.
Read this codeLost Communication with Multi-Axis Acceleration Sensor Module
A module on the network can no longer hear from the multi-axis acceleration sensor — the yaw/lateral-acceleration sensor used by stability control. Often a power, ground, or wiring fault, and stability and traction features typically disable themselves.
Read this codeLost Communication with Steering Angle Sensor Module
A module on the network can no longer hear from the steering angle sensor. Stability control and related systems usually disable themselves and warning lights come on. Usually a power, ground, wiring, or connector fault at the sensor.
Read this codeLost Communication With Tire Pressure Monitor Module
A module has stopped receiving messages from the tire pressure monitor (TPMS) module over the data network. TPMS warnings and live pressure readings may be unavailable, but core driving functions are unaffected.
Read this codeLost Communication with Park Brake Control Module
A module on the network can no longer hear from the park brake control module, which operates the electronic parking brake. Usually a power, ground, or wiring fault, it can leave the parking brake stuck applied or released and light the brake and EPB warnings.
Read this codeLost Communication with Brake System Control Module
A module on the network can no longer hear from the brake system control module, which runs ABS and works with stability control. Usually a power, ground, or wiring fault, it typically disables ABS and stability control while leaving your base brakes working.
Read this codeLost Communication with Steering Effort Control Module
A module on the network can no longer hear from the steering effort control module, which manages power-steering assist. Usually a power, ground, or wiring fault, it can make the steering heavy or reduce assist and light the power-steering warning.
Read this codeLost Communication with Power Steering Control Module
A module on the network can no longer hear from the power steering control module. Steering assist may be reduced or lost and warning lights come on. Usually a power, ground, wiring, or connector fault at the steering module.
Read this codeLost Communication with Ride Level Control Module
A module on the network can no longer hear from the ride level (suspension height) control module. Usually a power, ground, or wiring fault, it can disable automatic leveling and air suspension and light a suspension warning.
Read this codeLost Communication With Active Roll Control Module
The active roll control (anti-roll) module has gone silent on the vehicle network — other modules expect its messages and aren't receiving them.
Read this codeLost Communication With Power Steering Control Module — Rear
The rear power steering (rear-steer) control module has stopped communicating on the vehicle network. Applies to vehicles with four-wheel/rear-wheel steering.
Read this codeLost Communication With Differential Control Module — Front
The front differential control module has gone silent on the network — common on 4WD/AWD vehicles with electronically controlled front axles or lockers.
Read this codeLost Communication with Rear Differential Control Module
A module on the network can no longer hear from the rear differential control module (electronic limited-slip / e-diff). Usually a power, ground, or wiring fault, it can disable torque vectoring and traction features and light a warning.
Read this codeLost Communication with Trailer Brake Control Module
Another module on the vehicle network can no longer hear from the integrated trailer brake controller. The truck itself drives normally, but the electric brakes on a towed trailer may not apply — which matters a great deal the moment you hitch something up.
Read this codeLost Communication with All Terrain Control Module
Another module on the vehicle network can no longer hear from the all-terrain / terrain-mode control module — the computer behind the drive-mode selector that retunes traction, throttle, and four-wheel-drive behavior for sand, mud, snow or rock. The vehicle still drives, but it drops back to its default on-road calibration.
Read this codeLost Communication with Suspension Control Module 'B'
Another module on the vehicle network can no longer hear from the second suspension control module. On a vehicle with air springs or adaptive dampers, the suspension falls back to a fixed default — which can mean a harsh ride, a vehicle that will not raise or level itself, or in the worst case a car sitting on its bump stops.
Read this codeLost Communication with Body Control Module (BCM)
A module on the network can no longer hear from the body control module — the computer that runs lighting, locks, windows, and other body electronics. Usually a power, ground, or wiring fault at the BCM.
Read this codeLost Communication with Body Control Module B (BCM B)
A module on the network can no longer hear from a second body control module. Body electrical features tied to that module may stop working and warning lights may appear. Usually a power, ground, wiring, or connector fault at the module.
Read this codeLost Communication with Body Control Module C
A module on the network can no longer hear from body control module C, an additional body controller on feature-rich vehicles. Usually a power, ground, or wiring fault, it can disrupt the body electronics that controller manages.
Read this codeLost Communication with Body Control Module D
A module on the network can no longer hear from body control module D, an additional body controller on feature-rich vehicles. Usually a power, ground, or wiring fault, it can disrupt the body electronics that controller manages.
Read this codeLost Communication with Body Control Module E
A module on the network can no longer hear from body control module E, an additional body controller on feature-rich vehicles. Usually a power, ground, or wiring fault, it can disrupt the body electronics that controller manages.
Read this codeLost Communication with Body Control Module F
A module on the network can no longer hear from body control module F, an additional body controller on feature-rich vehicles. Usually a power, ground, or wiring fault, it can disrupt the body electronics that controller manages.
Read this codeLost Communication With Gateway A
A module on the network can no longer hear from the gateway module that routes messages between the vehicle's communication buses. Because the gateway connects the networks, this can cause widespread communication faults. Usually a power, ground, wiring, or connector fault at the gateway.
Read this codeLost Communication With Gateway B
A module on the network can no longer hear from gateway module 'B', one of the hubs that route messages between the vehicle's communication buses. Because a gateway bridges the networks, this can cause widespread communication faults. Usually a power, ground, wiring, or connector fault at the gateway.
Read this codeLost Communication With Gateway C
A module on the network can no longer hear from gateway module 'C', one of the hubs that route messages between the vehicle's communication buses. Because a gateway bridges the networks, this can cause widespread communication faults. Usually a power, ground, wiring, or connector fault at the gateway.
Read this codeLost Communication With Gateway D
A module on the network can no longer hear from gateway module 'D', one of the hubs that route messages between the vehicle's communication buses. Because a gateway bridges the networks, this can cause widespread communication faults. Usually a power, ground, wiring, or connector fault at the gateway.
Read this codeLost Communication With Gateway E
A module on the network can no longer hear from gateway module 'E', one of the hubs that route messages between the vehicle's communication buses. Because a gateway bridges the networks, this can cause widespread communication faults. Usually a power, ground, wiring, or connector fault at the gateway.
Read this codeLost Communication with Restraints Control Module (Airbags)
A module on the network can no longer hear from the restraints control module — the airbag and seatbelt-pretensioner computer. The airbag warning light comes on and crash protection may be compromised. Diagnose promptly.
Read this codeLost Communication with Restraints Control Module B
A module on the network can no longer hear from restraints control module B, a secondary airbag/restraints controller. Usually a power, ground, or wiring fault, it can disable airbags and pretensioners and light the airbag warning.
Read this codeLost Communication With Side Restraints Control Module (Right)
The airbag system has stopped receiving messages from the right side restraints control module. Because this module manages the passenger-side side and curtain airbags, treat it as safety-critical and diagnose it promptly.
Read this codeLost Communication with Restraints Occupant Sensing Control Module
A module on the network can no longer hear from the occupant sensing / classification module that tells the airbag system who is in the seat. Usually a power, ground, or wiring fault, it can disable smart airbag features and light the airbag warning.
Read this codeLost Communication with Instrument Panel Cluster (IPC)
A module on the network can no longer hear from the instrument panel cluster — the gauges and warning-light display. Gauges may go dead or erratic. Usually a power, ground, or wiring fault at the cluster.
Read this codeLost Communication with Information Center / Display Module
A module on the network can no longer hear from the driver information center or display module — the screen that shows trip data, warnings, and settings. Usually a power, ground, fuse, wiring, or connector fault.
Read this codeLost Communication With Information Center "B"
The vehicle's secondary information display module ("B") has stopped communicating on the network — usually a power, ground, or connector issue at the display.
Read this codeLost Communication With Head-Up Display
The head-up display module has gone silent on the vehicle network — a dark or frozen HUD with the rest of the car working normally.
Read this codeLost Communication With Parking Assist Control Module
Another module on the network has stopped receiving messages from the parking assist control module — the unit that runs the parking sensors and, on some vehicles, the rear camera and automated parking. Usually a power, ground, wiring, or module fault.
Read this codeLost Communication With Audible Alert / Chime Control Module
Another module on the network has stopped receiving messages from the audible alert (chime) control module — the unit that produces warning chimes and buzzers. Usually a power, ground, wiring, or module fault.
Read this codeLost Communication With Compass Module
Another module on the network has stopped receiving messages from the compass module — the unit that supplies vehicle heading. Usually a power, ground, wiring, or module fault.
Read this codeLost Communication With Navigation Display Module
The screen unit has gone quiet on the bus. Because that same screen is the interface for the camera, the climate menus, the audio source and the vehicle settings, the customer usually describes this as five faults rather than one — and none of those other modules is broken.
Read this codeLost Communication With Navigation Control Module
The navigation computer is missing from the bus. It is usually mounted under a seat or in the cargo area, which means the two things that kill it are liquids and luggage — and neither of those is a wiring fault you find by tracing the harness.
Read this codeLost Communication with HVAC Control Module
A module on the network can no longer hear from the HVAC (heating, ventilation, and air conditioning) control module. Climate control may stop responding. Usually a power, ground, fuse, wiring, or connector fault.
Read this codeLost Communication With HVAC Control Module 'B'
A module on the network can no longer hear from the second HVAC (climate) control module — module 'B'. Often used on multi-zone or rear climate systems. Usually a power, ground, fuse, wiring, or connector fault.
Read this codeLost Communication With Auxiliary Heater Control Module
A module on the network can no longer hear from the auxiliary heater control module — the controller for a supplemental cabin or coolant heater. Cabin warm-up may be slow. Usually a power, ground, fuse, wiring, or connector fault.
Read this codeLost Communication With Vehicle Immobilizer Control Module
Another module has stopped receiving messages from the immobilizer control module — the anti-theft unit that authorizes engine start. Can cause a no-start, since the engine will not run without valid immobilizer authorization.
Read this codeLost Communication with Vehicle Security Control Module
A module on the network can no longer hear from the vehicle security / anti-theft control module. The immobilizer or alarm may misbehave and the engine may not start. Usually a power, ground, wiring, or connector fault.
Read this codeLost Communication With Sunroof Control Module
Another module on the network has stopped receiving messages from the sunroof control module — the unit that operates the power sunroof or moonroof. Usually a power, ground, wiring, or module fault.
Read this codeLost Communication With Restraints System Sensor A
The airbag controller has stopped receiving messages from restraints system sensor A — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor B
The airbag controller has stopped receiving messages from restraints system sensor B — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor C
The airbag controller has stopped receiving messages from restraints system sensor C — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor D
The airbag controller has stopped receiving messages from restraints system sensor D — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor E
The airbag controller has stopped receiving messages from restraints system sensor E — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor F
The airbag controller has stopped receiving messages from restraints system sensor F — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor G
The airbag controller has stopped receiving messages from restraints system sensor G — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor H
The airbag controller has stopped receiving messages from restraints system sensor H — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor I
The airbag controller has stopped receiving messages from restraints system sensor I — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication With Restraints System Sensor J
The airbag controller has stopped receiving messages from restraints system sensor J — a crash/impact sensor that feeds the airbag system. The airbag warning light will be on and deployment behavior may be affected.
Read this codeLost Communication with Radio
A module on the network can no longer hear from the radio/infotainment head unit. Audio, display, and connected features may stop working. Usually a power, ground, fuse, wiring, or connector fault at the radio.
Read this codeLost Communication With Antenna Control Module
The antenna control module has stopped talking on the network — typically showing up as dead radio reception, keyless-entry range problems, or both.
Read this codeLost Communication With Audio Amplifier
A module on the network — usually the radio/head unit — can no longer hear from the external audio amplifier. The sound system typically goes quiet or loses features. It's a comfort/convenience fault, not a driveability or safety problem.
Read this codeLost Communication With Steering Column Control Module
A module has stopped receiving messages from the steering column control module over the data network. This module handles steering-column functions like the clockspring, wheel controls, and often the steering-angle input, so features tied to it can be affected.
Read this codeLost Communication With Mirror Control Module
The mirror control module has gone silent on the network — power mirrors, folding, heating, memory, or auto-dim functions stop responding.
Read this codeLost Communication with Remote Function Actuation (RFA) Module
A module on the network can no longer hear from the Remote Function Actuation (RFA) module — the controller for keyless entry, remote start, and passive entry/push-button start. Remote and key-fob features may stop working.
Read this codeLost Communication With Cruise Control Front Distance Range Sensor
A module on the network can no longer hear from the front distance range sensor — the forward-facing radar that adaptive cruise control and collision-avoidance systems rely on. Those driver-assist features shut off, but normal driving is unaffected.
Read this codeInternal Control Module Software Incompatibility
A control module has detected that the software or calibration versions running across the vehicle's modules don't match what they expect. This is a programming/calibration mismatch — not a wiring fault — and is almost always tied to a recent module replacement, update, or reflash.
Read this codeSoftware Incompatibility With ECM/PCM
The powertrain controller is running a calibration the rest of the vehicle does not expect. Of every module that can throw a compatibility code, this is the one that also owns the anti-theft pairing — which is why a used replacement rarely just works.
Read this codeSoftware Incompatibility With Transmission Control Module
The transmission controller's calibration does not match the set the vehicle expects. Expect harsh shifting for a hundred miles after the fix — that is the adaptive memory relearning, not a failed repair.
Read this codeSoftware Incompatibility With Transfer Case Control Module
The transfer case controller is running a calibration that does not match the rest of the vehicle. Unlike most software-mismatch codes this one sits on top of a mechanical device with real physical positions, and a controller that misunderstands where the transfer case is can leave it between ranges.
Read this codeSoftware Incompatibility With Gear Shift Control Module
The gear shift control module's calibration does not match the rest of the vehicle. On a shift-by-wire car there is no cable between the lever and the gearbox, so this is the one code in the family with a parking and roll-away dimension — and the one that can stop the vehicle being towed conventionally.
Read this codeSoftware Incompatibility With Cruise Control Module
A calibration mismatch involving the cruise control module. Before anything else, find out what that module physically is on this vehicle — on many cars it is not a separate box at all, and on cars with adaptive cruise it is the forward radar or camera that also runs automatic braking.
Read this codeSoftware Incompatibility With Fuel Injector Control Module
The injector control module's calibration does not match the rest of the vehicle. This module is not just a switch — it holds the per-injector correction values that make cylinders deliver equal fuel, so a mismatch here produces a fault that feels mechanical and is not.
Read this codeSoftware Incompatibility With Glow Plug Control Module
A diesel-only code where the urgency depends on the calendar. In July it may produce no symptom at all; on the first freezing morning it can leave you unable to start the engine.
Read this codeSoftware Incompatibility With Throttle Actuator Control Module
A module has detected that the throttle actuator control module is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch — not a wiring fault — usually following a throttle module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Alternative Fuel Control Module
A module has detected that the alternative fuel control module (CNG, LPG, or other gaseous-fuel system controller) is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch — not a wiring fault — usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Fuel Pump Control Module
The fuel pump control module is running a calibration that does not belong with the rest of the vehicle's software. Of all the software-incompatibility codes, this is the one most likely to leave you at the roadside, because the mismatched data is a pressure map rather than a comfort setting.
Read this codeSoftware Incompatibility With Drive Motor Control Module
A module has detected that the drive motor control module (the inverter/motor controller in a hybrid or electric vehicle) is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch — not a wiring fault — usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Battery Energy Control Module A
A module has detected that battery energy control module 'A' — the high-voltage battery management controller on a hybrid or EV — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Battery Energy Control Module B
A module has detected that battery energy control module 'B' — a second high-voltage battery management controller on a hybrid or EV — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Four-Wheel Drive Clutch Control Module
A module has detected that the four-wheel drive clutch control module is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch — not a wiring fault — usually following a 4WD/AWD module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Anti-Lock Brake System (ABS) Control Module
The ABS controller is running a calibration the rest of the car does not accept. Because that module also publishes wheel speed to half the vehicle, the complaints it produces often have nothing to do with braking.
Read this codeSoftware Incompatibility With Vehicle Dynamics Control Module
The stability control module's calibration does not match this vehicle. Its calibration encodes physical properties like track width and suspension tune, so a correct part number from a different trim is still the wrong software.
Read this codeSoftware Incompatibility With Park Brake Control Module
Another module has judged the electronic parking brake controller to be running software that does not belong on this vehicle. What makes this one different from the rest of the software-incompatibility family is that there is usually no mechanical fallback: if the brake ends up applied and the module will not release it, the car cannot be moved without a tool.
Read this codeSoftware Incompatibility With Brake System Control Module
The brake controller is running a software version the rest of the vehicle does not recognise. Of every member of this family, this is the one where the network's response — shutting down features rather than tolerating an unknown version — is the point.
Read this codeSoftware Incompatibility With Steering Effort Control Module
The steering effort controller's calibration does not match what this vehicle expects. The trap here is that a matching part number is not a matching calibration — steering maps are tuned to the car's physical specification, not just to its model name.
Read this codeSoftware Incompatibility With Power Steering Control Module
The power steering controller's software does not match the vehicle's approved set. This is the family member most often created by the repair itself, because an electric steering module draws enough current to sag a weak battery mid-flash.
Read this codeSoftware Incompatibility With Ride Level Control Module
The ride height controller is running a calibration the rest of the vehicle does not recognise. This is the software-incompatibility code where the module is most often genuinely built for a different version of the same car — and the one where leaving it alone can burn out the compressor while you wait.
Read this codeSoftware Incompatibility With Body Control Module
Another module has judged the body control module's software wrong for this vehicle. The trap here is that software and configuration are two separate things — this code only checks one of them, so a correct flash with the wrong option data clears the code and leaves the features broken.
Read this codeSoftware Incompatibility With Instrument Panel Control Module
The gauge cluster is running a software version the rest of the vehicle does not accept. Its severity rating understates it, because this is the module every other module speaks through — a mismatched cluster can quietly fail to show you a warning that a perfectly healthy system is trying to raise.
Read this codeSoftware Incompatibility With HVAC Control Module
The climate controller is running a version the rest of the vehicle does not accept. On a combustion car that is largely a comfort complaint — but on a hybrid or an electric vehicle the same module cools the traction battery, which turns this into a charging and power fault rather than a comfort one.
Read this codeSoftware Incompatibility With Auxiliary Heater Control Module
The auxiliary heater controller is running software the vehicle does not recognise. It reads like a comfort fault, but the appliance behind it is usually a fuel-fired burner or a high-voltage heating element — and it is often a retrofit that was never coded in the first place.
Read this codeSoftware Incompatibility With Vehicle Immobilizer Control Module
A module has detected that the vehicle immobilizer control module — the anti-theft controller that authenticates the key/fob before allowing the engine to start — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Vehicle Security Control Module
A module has detected that the vehicle security control module — the controller behind the alarm system, keyless entry, and anti-theft door locking — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Steering Angle Sensor Module
A module has detected that the steering angle sensor module — which reports how far and how fast the steering wheel is turned to stability control, power steering, and ADAS systems — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Steering Column Control Module
A module has detected that the steering column control module — which manages functions like electric tilt/telescope, steering lock, and column-mounted controls — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Tire Pressure Monitor Module
A module has detected that the tire pressure monitor (TPMS) module — which reads each tire's pressure sensor and controls the low-tire-pressure warning light — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring or sensor fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Body Control Module 'A'
The letter means this vehicle has more than one body controller. On a split architecture the modules are version-coupled to each other, so updating only the one named in the code usually just moves the fault to its partner — and the pattern of what still works tells you which module is out of step before you scan anything.
Read this codeSoftware Incompatibility With Multi-axis Acceleration Sensor Module 'A'
A module has detected that multi-axis acceleration sensor module A — which measures lateral, longitudinal, and/or vertical acceleration for stability control and ride/handling systems — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Gear Shift Control Module 'B'
A module has detected that gear shift control module B — the second of two shift-related controllers on vehicles with split or redundant shift-by-wire/gear-selector electronics — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Radio
A module has detected that the radio/infotainment head unit is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a head unit replacement, update, or reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Pack Sensor Module
On a hybrid or electric vehicle, a module has detected that the high-voltage battery pack sensor module — which monitors individual cell voltages, temperatures, and pack current — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a battery service, module replacement, or reflash.
Read this codeSoftware Incompatibility With Restraints Control Module
A module has detected that the restraints control module (airbag control module) is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, but because this module governs airbag and seatbelt pretensioner deployment, it's treated as a high-priority, safety-relevant code.
Read this codeSoftware Incompatibility With Battery Charger Control Module A
On a plug-in hybrid or electric vehicle, a module has detected that battery charger control module A — the onboard charger that converts AC power from a wall outlet or charging station into DC power for the high-voltage battery — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a charger module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Remote Function Actuation Module
A module has detected that the remote function actuation (RFA) module — which handles keyless entry, key fob commands, and often remote start and passive entry — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Body Control Module 'B'
A module has detected that body control module B — the second of two body electronics controllers on vehicles with split BCM architecture — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a module replacement, update, or reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module A
On a hybrid or electric vehicle, a module has detected that battery interface control module A — which handles high-voltage contactor control and the connection between the battery pack and the rest of the powertrain — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a battery service, module replacement, or reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module B
On a hybrid or electric vehicle, a module has detected that battery interface control module B — the second of two contactor/interface controllers on vehicles with a more complex or dual-pack high-voltage architecture — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following a battery service, module replacement, or reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module C
On a hybrid or electric vehicle with a multi-segment high-voltage battery architecture, a module has detected that battery interface control module C is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module D
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module D is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module E
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module E is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module F
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module F is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module G
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module G is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module H
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module H is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module I
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module I is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module J
On a hybrid or electric vehicle with a multi-segment high-voltage battery pack, a module has detected that battery interface control module J is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, usually following battery service, module replacement, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module K
On a hybrid or electric vehicle with a heavily segmented high-voltage battery pack, a module has flagged battery interface control module K as running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, and usually follows battery service, a module swap, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module L
On a hybrid or electric vehicle with a heavily segmented high-voltage battery pack, battery interface control module L has been found to be running a software or calibration version that doesn't match the rest of the vehicle's modules. This is a programming mismatch rather than a wiring or communication failure, typically appearing after battery service, a module swap, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module M
On a hybrid or electric vehicle with a heavily segmented high-voltage battery pack, battery interface control module M is running a software or calibration version that doesn't match the rest of the vehicle's modules. This points to a programming mismatch rather than a wiring problem, and typically follows battery service, a module swap, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module N
On a hybrid or electric vehicle with a heavily segmented high-voltage battery pack, battery interface control module N has been found running a software or calibration version outside the set the rest of the vehicle's modules expect. This is a programming mismatch, not a wiring fault, typically appearing after battery service, a module swap, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module O
On a hybrid or electric vehicle with a heavily segmented high-voltage battery pack, battery interface control module O has been found running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch rather than a wiring fault, and it typically shows up after battery service, a module swap, or a reflash.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Interface Control Module P
On a hybrid or electric vehicle with an unusually heavily segmented high-voltage battery pack, battery interface control module P — the final module in this lettered series — has been found running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch rather than a wiring fault, typically following battery service, a module swap, or a reflash.
Read this codeSoftware Incompatibility With Engine Disconnect Clutch
On a hybrid vehicle whose gasoline engine can be mechanically coupled to and decoupled from the drivetrain, the module that controls the engine disconnect clutch is running software or a calibration that doesn't match the rest of the vehicle's modules. This is a programming mismatch rather than a wiring fault, and it typically follows transmission or hybrid drivetrain service.
Read this codeSoftware Incompatibility With Brake Booster Control
The module that controls the vehicle's electric brake booster is running software or a calibration that doesn't match the rest of the vehicle's modules. This is a programming mismatch rather than a mechanical brake fault, but because it involves brake pedal assist, it should be treated as a higher-priority repair even though the vehicle typically remains driveable.
Read this codeSoftware Incompatibility With Battery Energy Control Module C
A module has detected that battery energy control module 'C' — one of the controllers that manages the high-voltage battery on a hybrid or EV — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a wiring fault, and usually follows a module replacement, pack service, update, or reflash.
Read this codeSoftware Incompatibility With Vehicle Thermal Management Control Module
The module that coordinates cooling and heating across the engine, transmission, battery, and cabin systems is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch rather than a mechanical cooling-system fault, and it usually follows a module replacement or software update.
Read this codeSoftware Incompatibility With Active Grille Air Shutter Module A
The module that opens and closes the vehicle's active grille shutters — the movable vanes behind the front grille that improve aerodynamics and warm-up time — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, and the vehicle remains fully driveable.
Read this codeSoftware Incompatibility With Active Grille Air Shutter Module B
The module that opens and closes a second set of active grille shutters — motorized vanes behind the grille that improve aerodynamics and warm-up time — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, and the vehicle remains fully driveable.
Read this codeSoftware Incompatibility With Active Grille Air Shutter Module C
The module that opens and closes a third set of active grille shutters — motorized vanes behind the grille that improve aerodynamics and warm-up time — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, and the vehicle remains fully driveable.
Read this codeSoftware Incompatibility With Active Grille Air Shutter Module D
The module that opens and closes a fourth set of active grille shutters — motorized vanes behind the grille that improve aerodynamics and warm-up time — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, and the vehicle remains fully driveable.
Read this codeSoftware Incompatibility With NOx Sensor C
A third nitrogen oxide (NOx) sensor module used for diesel or lean-burn emissions control is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, not a failed sensor, but because it affects emissions monitoring it should be treated as more than a cosmetic issue.
Read this codeSoftware Incompatibility With Ion Sense Module
The module that uses ion-sensing technology to monitor combustion — detecting misfire, knock, or air-fuel conditions through the spark plug circuit itself rather than a separate sensor — is running software or a calibration that doesn't match the rest of the vehicle's modules. It's a programming mismatch, and the vehicle usually remains driveable.
Read this codeSoftware Incompatibility With Hybrid/EV Battery Inductive Charger Control Module
The module that manages wireless (inductive) charging of the hybrid or EV high-voltage battery is communicating on the network, but its software or calibration doesn't match what the rest of the vehicle's modules expect. It's a programming mismatch, not a wiring fault, and the vehicle usually remains driveable.
Read this codeInvalid Data Received from ECM/PCM A
Another module is hearing the engine controller perfectly well but has rejected what it said. Because almost every module on the vehicle listens to the engine controller, this code tends to show up in several places at once — and that pattern is the most useful clue it gives you.
Read this codeInvalid Data Received from Transmission Control Module
The transmission controller is still talking but what it reports has been rejected as impossible. Before any of this is treated as an electrical problem, check the fluid — a transmission low on fluid genuinely does behave in ways its own controller cannot describe sensibly.
Read this codeInvalid Data Received From Transfer Case Control Module
A module is receiving messages from the transfer case control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Common on 4WD/AWD trucks and SUVs after sensor faults, low voltage, or module programming issues.
Read this codeInvalid Data Received From Gear Shift Control Module A
A module is receiving messages from the gear shift control module — the electronic shifter on shift-by-wire vehicles — but the data is implausible or out of range. Because gear selection is safety-relevant, many vehicles react conservatively, sometimes refusing to shift out of Park.
Read this codeInvalid Data Received From Cruise Control Module
A module is receiving messages from the cruise control module, but the data is implausible or out of range. Cruise control typically disables itself as a precaution. The car drives normally otherwise — this is a convenience-system fault, not a driveability emergency.
Read this codeInvalid Data Received From Fuel Injector Control Module
A module is receiving messages from the fuel injector control module (FICM), but the data is implausible or out of range. Most common on diesels with a dedicated injector driver module. Can cause hard starts, rough running, or reduced power depending on which data is invalid.
Read this codeInvalid Data Received From Glow Plug Control Module 1
A module is receiving messages from the glow plug control module on a diesel engine, but the data is implausible or out of range. The usual result is hard cold starting and a glow plug warning light. A diesel-only code — the connection is alive, the content is wrong.
Read this codeInvalid Data Received From Throttle Actuator A Control Module
A module is receiving messages from the throttle actuator control module, but the data is implausible or out of range. Because throttle control is safety-relevant, the vehicle typically responds with reduced power or limp mode until the data can be trusted again.
Read this codeInvalid Data Received From Alternative Fuel Control Module
A module is receiving messages from the alternative fuel control module, but the data inside them is implausible or out of range. Seen on CNG, LPG/propane, and bi-fuel vehicles. The connection is alive — the content is wrong.
Read this codeInvalid Data Received From Air Conditioning (A/C) Control Module
A module is receiving messages from the air conditioning (A/C) control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Usually a comfort-only fault.
Read this codeInvalid Data Received From Exhaust Gas Recirculation Control Module 'A'
A module is receiving messages from exhaust gas recirculation (EGR) control module 'A', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Emissions-relevant.
Read this codeInvalid Data Received From Exhaust Gas Recirculation Control Module 'B'
A module is receiving messages from exhaust gas recirculation (EGR) control module 'B', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Emissions-relevant.
Read this codeInvalid Data Received From Turbocharger/Supercharger Control Module 'A'
A module is receiving messages from turbocharger/supercharger control module 'A', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Can affect boost and power.
Read this codeInvalid Data Received From Turbocharger/Supercharger Control Module 'B'
A module is receiving messages from turbocharger/supercharger control module 'B', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Can affect boost and power.
Read this codeInvalid Data Received From Reductant Control Module
A module is receiving messages from the reductant (diesel exhaust fluid) control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Seen on diesels with SCR emissions systems.
Read this codeInvalid Data Received From Fuel Pump Control Module
A module is receiving messages from the fuel pump control module, but the data inside them is implausible or out of range. Common on vehicles with an electronic returnless or demand-based fuel system. The connection is alive — the content is wrong.
Read this codeInvalid Data Received From Drive Motor Control Module
A module is receiving messages from the drive motor control module, but the data inside them is implausible or out of range. Found on hybrids and EVs, where this module runs the traction motor. The connection is alive — the content is wrong. High-voltage system: professional diagnosis.
Read this codeInvalid Data Received From Battery Energy Control Module A
A module is receiving messages from battery energy control module A, but the data inside them is implausible or out of range. Found on hybrids and EVs, where this module manages the high-voltage pack. The connection is alive — the content is wrong. High-voltage system: professional diagnosis.
Read this codeInvalid Data Received From Battery Energy Control Module B
A module is receiving messages from battery energy control module B, but the data inside them is implausible or out of range. Seen on hybrids and EVs that use more than one battery supervisor. The connection is alive — the content is wrong. High-voltage system: professional diagnosis.
Read this codeInvalid Data Received From Four-Wheel Drive Clutch Control Module
A module is receiving messages from the four-wheel-drive clutch control module, but the data inside them is implausible or out of range. Common on AWD/4WD vehicles with an electronically controlled coupling. The connection is alive — the content is wrong.
Read this codeInvalid Data Received from Anti-Lock Brake System (ABS) Control Module
A module is receiving messages from the ABS control module, but the data — wheel speeds or brake status — is implausible or out of range. The link is alive; the content is wrong. Often a wheel speed sensor, calibration, or internal ABS fault.
Read this codeInvalid Data Received from Vehicle Dynamics Control Module
A module is receiving messages from the vehicle dynamics (stability control) module, but the data — yaw, lateral acceleration, or stability status — is implausible or out of range. The link is alive; the content is wrong. Often a sensor, calibration, or internal fault.
Read this codeInvalid Data Received From Park Brake Control Module
A module is receiving messages from the electronic park brake control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Because it touches the parking brake and can affect ABS/stability data, treat it seriously.
Read this codeInvalid Data Received from Brake System Control Module
A module is receiving messages from the brake system control module (ABS/ESC), but the data is implausible or out of range. The connection is alive — the content is wrong. Often a wheel-speed sensor, calibration, or internal fault driving bad data, or a network issue corrupting it.
Read this codeInvalid Data Received From Steering Effort Control Module
A module is receiving messages from the steering effort control module, but the data inside them is implausible or out of range. This module tunes power-steering assist. The connection is alive — the content is wrong.
Read this codeInvalid Data Received From Battery Isolation/Voltage Stabilization Control Module
A module that manages battery isolation or voltage stabilization is sending data the rest of the network doesn't believe — talking, but not making sense.
Read this codeInvalid Data Received From Exhaust Gas Sensor Module
A module is receiving messages from the exhaust gas sensor module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong.
Read this codeInvalid Data Received From Rocker Arm Control Module 'A'
A module is receiving messages from rocker arm control module 'A', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Related to variable valve lift and cylinder deactivation systems.
Read this codeInvalid Data Received From Rocker Arm Control Module 'B'
A module is receiving messages from rocker arm control module 'B', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. This is the 'B' counterpart to U041C.
Read this codeInvalid Data Received From All Wheel Drive Control Module
A module is receiving messages from the all-wheel drive control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong.
Read this codeInvalid Data Received From Electronic Throttle System Control Module "B"
A second throttle-control module ("B") is sending data the network doesn't believe. Rare hardware — mostly multi-throttle or specialized powertrains.
Read this codeInvalid Data Received From Power Steering Control Module A
A module is receiving messages from the power steering control module, but the data is implausible or out of range. Electric power steering may reduce or suspend assist as a precaution — the wheel gets heavy but the car still steers. The connection is alive; the content is wrong.
Read this codeInvalid Data Received From Suspension Control Module 'A'
A module is receiving messages from suspension control module 'A', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Seen on vehicles with adaptive dampers or air suspension.
Read this codeInvalid Data Received from Body Control Module
A module is receiving messages from the body control module (BCM), but the data is implausible or out of range. The connection is alive — the content is wrong. Often a switch, sensor, calibration, or internal fault driving bad data, or a network issue corrupting it.
Read this codeInvalid Data Received from Instrument Panel Control Module
A module is still hearing from the instrument panel cluster (IPC), but the data inside those messages is implausible or out of range. The link is alive — the content is wrong. Usually a sensor input, calibration, or internal cluster fault, or a network issue corrupting the data.
Read this codeInvalid Data Received from HVAC Control Module
A module is still hearing from the HVAC (heating, ventilation, and air conditioning) control module, but the data is implausible or out of range. The link is alive — the content is wrong. Usually a climate sensor, calibration, or internal fault, or a network issue corrupting the data.
Read this codeInvalid Data Received From Auxiliary Heater Control Module
A module is receiving messages from the auxiliary heater control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. A comfort-system fault, rarely a driveability problem.
Read this codeInvalid Data Received from Immobilizer / Vehicle Security Control Module
A module is receiving messages from the immobilizer / vehicle security control module, but the data is implausible, out of range, or fails authentication. The connection is alive — the content is wrong. Often a key, calibration, or programming fault, or a network issue corrupting it.
Read this codeInvalid Data Received From Vehicle Security Control Module
A module is receiving messages from the vehicle security control module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Can affect the anti-theft system and, occasionally, starting.
Read this codeInvalid Data Received from Steering Angle Sensor Module
A module is still hearing from the steering angle sensor, but the steering-position data is implausible or out of range. The link is alive — the content is wrong. Often an uncalibrated or failing sensor, or a network issue corrupting the data. Stability and steering-assist features may disable themselves.
Read this codeInvalid Data Received from Steering Column Control Module
A module is still hearing from the steering column control module, but the data is implausible or out of range. The link is alive — the content is wrong. Often a column sensor, calibration, or internal fault, or a network issue corrupting the data. Steering and stability features may disable themselves.
Read this codeInvalid Data Received From V2X Module
A module is receiving messages from the V2X (vehicle-to-everything) communication module, but the data inside them is implausible or out of range. The connection is alive — the content is wrong. A connectivity/telematics fault.
Read this codeInvalid Data Received From Chassis Control Module 'A'
A module is receiving messages from chassis control module 'A', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Can affect ride, handling, and stability features.
Read this codeInvalid Data Received From Chassis Control Module 'B'
A module is receiving messages from chassis control module 'B', but the data inside them is implausible or out of range. The connection is alive — the content is wrong. Can affect ride, handling, and stability features.
Read this codeInvalid Data Received From Active Vibration Control Module
A module is receiving messages from the active vibration control module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Mostly affects ride smoothness and cabin noise, not driveability.
Read this codeInvalid Data Received From Generator Control Module 'A'
A module is receiving messages from generator (charging) control module 'A', but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect charging and electrical stability.
Read this codeInvalid Data Received From Camshaft Position Control Module
A module is receiving messages from the camshaft position control module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect variable valve timing and driveability.
Read this codeInvalid Data Received From Tire Pressure Monitor Module
A module is receiving messages from the tire pressure monitor (TPMS) module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. A monitoring-only fault that does not affect driveability.
Read this codeInvalid Data Received From Body Control Module 'A'
A module is receiving messages from body control module 'A', but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect a wide range of body electrical features.
Read this codeInvalid Data Received From Multi-axis Acceleration Sensor Module 'A'
A module is receiving messages from the multi-axis acceleration sensor module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can disable stability control and related safety systems.
Read this codeInvalid Data Received From Cruise Control Front Distance Range Sensor
A module is receiving messages from the cruise control front distance range sensor, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can disable adaptive cruise and forward-collision features.
Read this codeInvalid Data Received From Active Roll Control Module
A module is receiving messages from the active roll control module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect body-roll control and handling in corners.
Read this codeInvalid Data Received From Power Steering Control Module (Rear)
A module is receiving messages from the rear power steering control module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can reduce or disable rear steering assist.
Read this codeInvalid Data Received From Differential Control Module (Front)
Messages from the front differential controller are arriving but their contents are implausible. Before anything else, establish whether this vehicle has a separate front differential at all — on a great many all-wheel-drive cars the front unit lives inside the transaxle, and that single fact changes the fluid, the price and the repair.
Read this codeInvalid Data Received From Differential Control Module (Rear)
The rear differential controller is broadcasting values another module has rejected as implausible. On the large number of crossovers using a clutch-type rear coupling, the leading root cause is not a failed part at all — it is a fluid and filter service interval almost no owner has heard of.
Read this codeInvalid Data Received From Trailer Brake Control Module
A module is receiving messages from the trailer brake control module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect integrated trailer braking while towing.
Read this codeInvalid Data Received From All Terrain Control Module
A module is receiving messages from the all terrain control module, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect terrain drive modes and off-road assist features.
Read this codeInvalid Data Received From Suspension Control Module 'B'
A module is receiving messages from suspension control module 'B', but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect ride height, damping, and handling.
Read this codeInvalid Data Received From Cruise Control Front Distance Range Sensor (Left)
The left forward radar is talking, but what it says does not hold up. The trap in this code is that plausibility is judged by comparison against the other sensor — so the unit the code names is not always the unit that is wrong.
Read this codeInvalid Data Received From Cruise Control Front Distance Range Sensor (Right)
A module is receiving messages from the right front distance range sensor, but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can disable adaptive cruise and forward safety features.
Read this codeInvalid Data Received From Accelerator Pedal Module
A module — usually the engine computer — is receiving messages from the accelerator pedal module, but the throttle-demand data inside them is implausible or out of range. The link is alive; the content is wrong. The vehicle may drop into a reduced-power fail-safe.
Read this codeInvalid Data Received From Vacuum Sensor A
A module is receiving messages from vacuum sensor 'A', but the pressure/vacuum data inside them is implausible or out of range. The link is alive; the content is wrong. Can affect brake-boost, EVAP, or boost-related monitoring depending on the vehicle.
Read this codeInvalid Data Received From Vacuum Sensor B
A module is receiving messages from vacuum sensor 'B', but the pressure/vacuum data inside them is implausible or out of range. The 'B' counterpart to U043E — same fault pattern, a second sensor location or system.
Read this codeInvalid Data Received From Pedestrian Alert Control Module
A module is receiving messages from the pedestrian alert control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Affects the low-speed warning sound on hybrids and EVs, not core driving.
Read this codeInvalid Data Received From Emissions Critical Control Information
A module is receiving emissions-critical control information over the network, but the data inside those messages is implausible or out of range. The link is alive; the content is wrong. Can affect emissions monitoring and readiness.
Read this codeInvalid Data Received From ECM/PCM 'B'
A module is receiving messages from the secondary engine/powertrain computer (ECM/PCM 'B'), but the data inside them is implausible or out of range. The link is alive; the content is wrong. The 'B' counterpart to U0401.
Read this codeInvalid Data Received From Body Control Module 'B'
A module is receiving messages from body control module 'B', but the data inside them is implausible or out of range. The link is alive; the content is wrong. The 'B' counterpart to U0431 — a second body controller on vehicles that use more than one.
Read this codeInvalid Data Received From Body Control Module 'C'
A module is receiving messages from body control module 'C', but the data inside them is implausible or out of range. The link is alive; the content is wrong. The 'C' counterpart to U0431/U0443 — a third body controller on feature-rich vehicles.
Read this codeInvalid Data Received From Body Control Module 'D'
A module is receiving messages from body control module 'D', but the data inside them is implausible or out of range. The link is alive; the content is wrong. The 'D' counterpart to U0431/U0443/U0444 — a fourth body controller on very feature-rich vehicles.
Read this codeInvalid Data Received From Body Control Module 'E'
A module is receiving messages from body control module 'E', but the data inside them is implausible or out of range. The link is alive; the content is wrong. The 'E' counterpart to U0431/U0443/U0444/U0445 — a fifth body controller on the most complex vehicles.
Read this codeInvalid Data Received From Gateway 'A'
A module is receiving messages relayed by gateway 'A', but the data inside them is implausible or out of range. The link is alive; the forwarded content is wrong. Because a gateway bridges several networks, this code is very often secondary to a fault on one of the buses it connects.
Read this codeInvalid Data Received From Gateway 'B'
A module is receiving messages relayed by gateway 'B', but the data inside them is implausible or out of range. The link is alive; the forwarded content is wrong. The 'B' counterpart to U0447 — a second gateway on vehicles that split routing across more than one.
Read this codeInvalid Data Received From Gateway 'C'
A module is receiving messages relayed by gateway 'C', but the data inside them is implausible or out of range. The link is alive; the forwarded content is wrong. The 'C' counterpart to U0447/U0448 — a third gateway on vehicles that split routing across several.
Read this codeInvalid Data Received From Gateway 'D'
A module is receiving messages relayed by gateway 'D', but the data inside them is implausible or out of range. The link is alive; the forwarded content is wrong. The 'D' counterpart to U0447/U0448/U0449 — a fourth gateway on the most network-heavy vehicles.
Read this codeInvalid Data Received From Gateway 'E'
A module is receiving messages relayed by gateway 'E', but the data inside them is implausible or out of range. The link is alive; the forwarded content is wrong. The 'E' counterpart to U0447-U044A — the fifth gateway, and the one whose number jumps past the reserved gap to U0451.
Read this codeInvalid Data Received From Restraints Control Module
A module is receiving messages from the restraints (airbag/SRS) control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Because this module governs airbags and seatbelt pretensioners, treat it as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Side Restraints Control Module (Left)
The left side restraints module is still talking, but the numbers in its messages are implausible. On a left-hand-drive vehicle that is the driver's side — the seat that is occupied on every trip and moved more than any other, which is why this side's harness fails from motion rather than from neglect.
Read this codeInvalid Data Received From Side Restraints Control Module (Right)
Implausible data from the right side restraints module. This is the side that carries occupant classification, so the complaint often arrives as a passenger airbag indicator behaving oddly rather than as an SRS lamp — and liquid spilled into the footwell is a leading cause here that has no equivalent opposite it.
Read this codeInvalid Data Received From Restraints Occupant Classification System Module
A module is receiving messages from the occupant classification system (OCS) module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Because this module decides whether the passenger airbag is enabled or suppressed, treat it as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Coolant Temperature Control Module
A module is receiving messages from the coolant temperature control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Because this data drives cooling and warm-up decisions, address it before it leads to poor temperature control or overheating.
Read this codeInvalid Data Received From Information Center 'A'
A module is receiving messages from the information center (driver information display) 'A', but the data inside them is implausible or out of range. The link is alive; the content is wrong. It affects displayed information and menus, not how the car drives.
Read this codeInvalid Data Received From Information Center 'B'
A module is receiving messages from the information center (driver information display) 'B', but the data inside them is implausible or out of range. The link is alive; the content is wrong. It affects displayed information, not how the car drives.
Read this codeInvalid Data Received From Head Up Display
A module is receiving messages from the head-up display (HUD), but the data inside them is implausible or out of range. The link is alive; the content is wrong. It affects the HUD projection, not how the car drives.
Read this codeInvalid Data Received From Parking Assist Control Module 'A'
A module is receiving messages from the parking assist control module 'A', but the data inside them is implausible or out of range. The link is alive; the content is wrong. Core driving is unaffected, but the parking aid may be disabled until it's fixed.
Read this codeInvalid Data Received From Anti-Lock Brake System (ABS) Control Module B
A module is receiving messages from a second ABS control module ('B'), but the data — wheel speeds or brake status — is implausible or out of range. The link is alive; the content is wrong. Base braking still works, but ABS and stability control may switch off.
Read this codeInvalid Data Received From Power Steering Control Module 'B'
A module is receiving messages from a second power steering control module ('B'), but the data is implausible or out of range. Electric power steering may reduce or suspend assist as a precaution — the wheel gets heavy but the car still steers. The link is alive; the content is wrong.
Read this codeInvalid Data Received From Automated Driving System Control Module A
A module is receiving messages from the automated driving system (ADS) control module 'A', but the data inside them is implausible or out of range. The link is alive; the content is wrong. Automated and hands-free driving features are disabled as a precaution — you must drive manually until it's fixed.
Read this codeInvalid Data Received From Automated Driving System Control Module B
A module is receiving messages from the automated driving system (ADS) control module 'B', but the data inside them is implausible or out of range. The link is alive; the content is wrong. Automated and hands-free driving features are disabled as a precaution — you must drive manually until it's fixed.
Read this codeInvalid Data Received From Automated Driving System Interface Module 'A'
A module is receiving messages from the automated driving system (ADS) interface module 'A', but the data inside them is implausible or out of range. The link is alive; the content is wrong. Automated and hands-free driving features are disabled as a precaution — you drive manually until it's fixed.
Read this codeInvalid Data Received From Automated Driving System Interface Module 'B'
A module is receiving messages from the automated driving system (ADS) interface module 'B', but the data inside them is implausible or out of range. The link is alive; the content is wrong. Automated and hands-free driving features are disabled as a precaution — you drive manually until it's fixed.
Read this codeInvalid Data Received From Audible Alert Control Module
A module is receiving messages from the audible alert (chime/warning-sound) control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. The main risk is missed or false warning chimes — the car drives normally.
Read this codeInvalid Data Received From Compass Module
A module is receiving messages from the compass module, but the data — the vehicle's heading — is implausible or out of range. The link is alive; the content is wrong. It affects the compass/direction display only; the car drives normally.
Read this codeInvalid Data Received From Navigation Display Module
A module is receiving messages from the navigation display module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. It affects the navigation/display screen only; the car drives normally.
Read this codeInvalid Data Received From Navigation Control Module
A module is receiving messages from the navigation control module, but the data — position, route, or guidance information — is implausible or out of range. The link is alive; the content is wrong. Navigation may misbehave; the car drives normally.
Read this codeInvalid Data Received From PTO Control Module
A module is receiving messages from the power take-off (PTO) control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. PTO-driven equipment may be disabled as a fail-safe; the truck itself drives normally.
Read this codeInvalid Data Received From HVAC Control Module – Rear
A module is receiving messages from the rear HVAC control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Rear heating/cooling may misbehave; the car drives normally.
Read this codeInvalid Data Received From Fuel Additive Control Module
A module is receiving messages from the fuel additive control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Found on diesels that dose additive for DPF regeneration; the car drives normally, but emissions health is at stake.
Read this codeInvalid Data Received From Fuel Cell Control Module
A module is receiving messages from the fuel cell control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Applies to hydrogen fuel-cell vehicles; power output may be limited as a fail-safe.
Read this codeInvalid Data Received From Starter/Generator Control Module
A module is receiving messages from the starter/generator control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Found on start-stop and mild-hybrid vehicles; starting and charging functions are at stake.
Read this codeInvalid Data Received From Sunroof Control Module
A module is receiving messages from the sunroof control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. The sunroof may stop responding or lose one-touch features; the car drives normally.
Read this codeInvalid Data Received From Restraints System Sensor A
The airbag (restraints) control module is still hearing from restraints system sensor A, but the data in its messages is implausible or out of range. The link is alive; the content can't be trusted. Because this feeds airbag deployment decisions, treat it as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor B
The airbag (restraints) control module is receiving messages from restraints system sensor B, but the data is implausible or out of range. Communication is intact; the values are wrong. Because this sensor feeds airbag deployment logic, treat it as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor C
A module is receiving messages from restraints system sensor C, but the values are implausible or out of range. The sensor is talking; the data can't be trusted. Because it feeds airbag deployment decisions, treat U0473 as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor D
The airbag (restraints) control module still hears from restraints system sensor D, but the data is implausible or out of range and gets rejected. Communication is fine; the values are not. Because this sensor informs airbag deployment, treat U0474 as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor E
A module is receiving messages from restraints system sensor E, but the data is implausible or out of range. The link is alive; the values can't be trusted. Because this sensor feeds airbag deployment logic, treat U0475 as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor F
The airbag (restraints) control module is receiving messages from restraints system sensor F, but the values are implausible or out of range and get rejected. The sensor is talking; the data can't be trusted. Because it feeds airbag deployment, treat U0476 as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor G
A module is receiving messages from restraints system sensor G, but the data is implausible or out of range. Communication is intact; the values are not. Because this sensor feeds airbag deployment decisions, treat U0477 as safety-critical and diagnose it promptly.
Read this codeInvalid Data Received From Restraints System Sensor H
The airbag (restraints) control module still hears from restraints system sensor H, but the data is implausible or out of range and gets rejected. The link is alive; the values can't be trusted. Because this sensor informs airbag deployment, treat U0478 as safety-critical and diagnose it promptly.
Read this codeMain automotive tools
Pair a code lookup with the calculators to plan parts, labor, and your repair budget.
VIN Decoder & Vehicle Specs
Decode a VIN and view vehicle year, make, model, engine details, body style, manufacturing info, confidence notes, and verification checklist.
Car Payment Calculator
Estimate monthly auto loan payment, amount financed, total interest, taxes, fees, and total loan cost.
MPG & Fuel Cost Calculator
Estimate fuel cost, gallons used, cost per mile, and savings between vehicles with different MPG ratings.
Repair Cost Estimator
Estimate common car repair costs using repair type, vehicle category, parts, labor hours, and labor rate.
Car Value Estimator
Estimate a rough used car value range based on vehicle year, mileage, condition, vehicle type, and sale scenario.
Tire Size Calculator
Compare tire sizes, sidewall height, diameter, circumference, revolutions per mile, and speedometer impact.
Maintenance Cost Calculator
Estimate routine vehicle maintenance costs, monthly budget, annual cost, cost per mile, and service milestones.
About this code library
AutoLogicTools code pages provide general OBD-II trouble code information for planning conversations with a mechanic. A scan-tool reading is only the starting point. Verify diagnoses, parts, and labor with a qualified automotive professional before approving any repair.