OBD-II trouble code
P0182: Fuel 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.
Quick facts
- System
- Powertrain
- Category
- Fuel & Air
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $0 – $800
- DIY difficulty
- Intermediate DIY
What does P0182 mean?
The word "low" in this title describes voltage, not temperature, and the two run in opposite directions. A fuel temperature sensor is a negative-temperature-coefficient thermistor: hotter fuel means lower resistance, lower resistance pulls the signal line closer to ground, and the controller reads that low voltage as high heat. So P0182 — signal pinned near zero volts — decodes to fuel temperature pinned at the top of the calibration table. Owners who read the code title and expect a cold-related problem have it exactly backwards, and so does anyone who sees a scan tool reporting 150 °C and starts looking for an overheating cause.
That inversion is what makes this the consequential member of the block. Its siblings are largely inert: the controller loses an input, substitutes a default, and drives on. P0182 does not lose the input. It receives a confident, in-range, entirely wrong report that the fuel is dangerously hot — and on systems that act on fuel temperature, the controller does what it was designed to do about hot fuel. Common-rail diesels use fuel temperature in pump protection strategy and injection timing correction, and a false extreme reading can pull fuel quantity back, retard timing, or in some calibrations drop the engine into a reduced-power mode. Owners frequently arrive describing a power loss and never mention the light. Flex-fuel and returnless systems are milder about it, but the density compensation still moves the wrong way.
The cause list is shorter than it looks, because of one physical fact worth stating plainly: thermistors that fail internally overwhelmingly fail open, not shorted. The element cracks, a bond lets go, the leg corrodes through — all of which break the path rather than complete it. A signal wire pulled to ground means two conductors are touching that should not be, and the likeliest candidates are outside the sensor. Chafed insulation where the harness crosses a bracket or a fuel line. A connector holding water or fuel, which bridges the pins. A crushed lead. A pin pushed back in its housing and contacting the shell. On diesels, the sensor often lives on the filter housing or the injection pump, where the harness is routinely disturbed during filter changes and where spilled fuel softens insulation over the years.
The test that settles it takes under a minute and needs nothing but a scan tool. Unplug the sensor connector and watch the reported fuel temperature. With the sensor disconnected the circuit is open, so a healthy harness sends the reading to the extreme cold end of the scale. If it swings cold the moment you unplug, everything upstream of the connector is proven and the short is inside the sensor. If the reading stays pinned hot with nothing connected, the sensor is innocent and the short is between the connector and the module — and that is where you spend the next hour, wiggle-testing along the loom rather than ordering parts.
Common causes
- Signal wire shorted to ground through chafed insulation where the harness crosses a bracket, clip or fuel line
- Water, fuel or corrosion inside the connector bridging the signal and ground pins
- Terminal pushed back in the connector body and contacting the housing or an adjacent pin
- Internally shorted sensor — less common than a shorted harness, because thermistors usually fail open
- Crushed or pinched lead from previous fuel filter, pump or injection pump work
- Signal and ground wires shorted together inside the loom after long-term vibration
- Damaged wiring at the tank or filter housing where road spray and salt reach the harness
Symptoms
- Check engine light on, often accompanied by a genuine power complaint on diesels
- Fuel temperature in live data pinned at the top of the scale regardless of how long the engine has been off
- Reduced power or a derate on common-rail diesels that use fuel temperature in pump protection strategy
- Rough or long cranking when the density correction pushes fuelling the wrong way
- Noticeably worse fuel economy
- Emissions inspection rejected on the stored code
Diagnostic steps
- 1.Read the live fuel temperature on a cold engine. A reading at the top of the scale on a vehicle that has been parked overnight confirms the fault is present rather than historic.
- 2.Unplug the sensor connector and watch the reading. It should immediately swing to the extreme cold end. If it does, the short is inside the sensor.
- 3.If the reading stays pinned hot with the sensor disconnected, the short is in the harness between the connector and the module. Do not order a sensor.
- 4.Inspect the connector for water, fuel and green corrosion, and check that no terminal has been pushed back out of its lock.
- 5.Follow the harness looking for chafe points at brackets, clips and where the loom passes near the filter housing, injection pump or tank.
- 6.With the connector unplugged, measure resistance from the signal wire to chassis ground. A healthy circuit reads effectively open; a low reading confirms the short and tells you which section to isolate.
- 7.Check whether any other sensor sharing the same ground is misbehaving. A shared ground fault produces several odd readings at once and is a different repair.
- 8.On a diesel with a power complaint, confirm the derate clears once the circuit is repaired rather than assuming the two were unrelated.
Repair cost
$0 – $800
Diagnosis runs $75 to $150. A harness or connector repair — which is the more likely outcome here — is typically $90 to $280 depending on how far into the loom the damage runs. Replacing an accessible line or filter-housing mounted sensor is roughly $70 to $230 fitted. An in-tank sensor costs substantially more because of the access, not the part.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with wiring harness / circuit repair 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.