OBD-II trouble code
P0227: Throttle/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.
Quick facts
- System
- Powertrain
- Category
- Throttle / Idle
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $700
- DIY difficulty
- Intermediate DIY
What does P0227 mean?
On a drive-by-wire vehicle the control module reads several redundant position signals — typically two at the accelerator pedal and two inside the throttle body — and cross-checks them before acting on any throttle request. The letters identify those channels, and 'C' is the third one. Each channel normally reports a voltage inside a defined window, commonly around 0.5 volts at rest rising to roughly 4.5 volts at full travel, with exact figures varying by platform.
P0227 sets when the module sees the 'C' signal fall below its minimum threshold and stay there. That is a specific electrical condition with a short list of causes: the signal wire has found ground, the signal or reference wire has opened so nothing is being supplied, the 5-volt reference has been lost, or the sensor element itself has failed at the bottom of its range.
It is worth being precise about how this differs from its neighbors, because the four codes in the 'C' block are not interchangeable. P0225 is the general, non-directional circuit code. P0226 is range/performance — the signal is present and plausible on its own but does not agree with the other sensors. P0228 is the high-voltage fault. P0227 is specifically low. Knowing which one you have tells you what to test first, and on a low-voltage code that means checking whether the 5-volt reference is even reaching the sensor before you look at anything else.
There is a diagnostic subtlety here that catches people out. A low reading can be produced by three quite different faults that look identical on a scan tool: a short to ground, an open circuit, and a dead sensor all report near zero. Separating them takes one step — unplug the sensor and check whether the reference voltage is present at the connector. If the reference is there and the signal only goes low when the sensor is connected, the sensor or its internal path is the fault. If the reference is missing at the connector, the problem is upstream in the wiring or at the module, and no sensor will fix it.
Before any of that, confirm in service data which physical sensor your manufacturer designates 'C'. The letter assignment varies between platforms, and on a code from the less-common 'C' block, ordering the wrong part is the most expensive mistake available.
Because the module cannot trust a throttle-demand signal it knows is implausibly low, it enters a fail-safe state: throttle response is limited, RPM is capped, cruise control is disabled, and a companion code from the P2104 through P2110 group is usually stored alongside. The vehicle remains driveable but noticeably down on power.
Common causes
- Short to ground in the 'C' signal circuit
- Open or break in the signal, reference, or ground wire
- Lost or low 5-volt reference from the control module
- Corroded, loose, or disconnected connector at the pedal assembly or throttle body
- Failed position sensor element stuck at the bottom of its range
- Water intrusion into a connector or harness section
- Chafed harness where the signal wire has grounded against a bracket or body panel
- Spread, backed-out, or damaged terminal in the sensor connector
- Wiring damaged during recent intake, throttle body, or under-dash work
- Rodent damage to the engine-bay or under-dash harness
- Low system voltage from a weak battery or failing alternator
- Rarely, a control module with a failed internal input circuit
Symptoms
- Check engine light is on
- Reduced engine power warning on the dash
- Limp mode with throttle response capped regardless of pedal input
- Poor or delayed acceleration
- Rough or unstable idle
- Cruise control disabled
- Engine may stall or refuse to rev past a low RPM ceiling
- Companion codes such as P0225, P0226, or a P2104-P2110 fail-safe code
Diagnostic steps
- 1.Confirm in service data which physical sensor your manufacturer designates 'C', and confirm the vehicle actually has a third position channel, before ordering or testing anything.
- 2.Scan every module and record all stored and pending codes with freeze frame data. P0227 alone points at the 'C' circuit; P0227 stored with 'A' or 'B' codes points at something the sensors share, such as a common ground or the reference supply.
- 3.Test the battery and charging system first. Low system voltage drags every sensor reading down and can produce a low-voltage code on entirely healthy hardware.
- 4.Inspect the pedal and throttle-body connectors for moisture, green corrosion, bent or backed-out pins, and a properly seated locking tab. Reseat and re-test before going further.
- 5.With the key on and engine off, back-probe the 'C' signal wire. A reading pinned near zero confirms the code.
- 6.Unplug the sensor and check for the 5-volt reference at the connector. This one step separates the three faults that all read low: reference present means the sensor or its internal path is suspect, reference missing means the fault is upstream.
- 7.With the sensor still unplugged, check the signal wire for a short to ground and for continuity back to the control module.
- 8.Perform a loaded voltage-drop test on the sensor ground rather than an unloaded resistance check, which can hide a marginal connection.
- 9.Inspect the harness where it passes brackets, grommets, and hinge points for chafing that has grounded the signal wire, and wiggle-test with live data displayed.
- 10.Graph the 'C' signal alongside the other position channels while sweeping the pedal through full travel to confirm the channel is dead rather than merely offset.
- 11.If wiring, reference, and ground all test good, replace the affected pedal assembly or throttle body and perform the required relearn procedure.
Repair cost
$100 – $700
Diagnosis typically runs $75-$150. Wiring and connector repair is a common and relatively inexpensive outcome when the fault is a short to ground or a corroded pin, landing around $100-$350 with diagnostic time. An accelerator pedal position sensor or pedal assembly is roughly $150-$400 installed on mainstream vehicles. A throttle body is generally $250-$700 installed and higher on luxury platforms. A throttle or pedal relearn is required on most platforms afterward.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with accelerator pedal position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.