01 Why Your Car Battery Dies Unexpectedly (And How to Stop It … • 02 Why Engine Capacity Matters When Shopping For A New Car • 03 This Secret Driving Habit Can Quietly Destroy Your Brake Pa… • 04 Does Auto Start - Stop Wear Out a Starter? • 05 If You Cut a Car in Half, Will the Front Half Still Drive? • 06 People Admit They Ignored This Strange Noise Until Their En… • 07 Don't Panic! Understanding Why Water Is Coming From Your Ca… • 08 Why Do Car Engines Have a Redline and What Happens If You E… • 09 Exploring the Toyota 1NZ Engine: Features and Performance A… • 10 Fuel Efficiency Unleashed: 10 Hacks for Smart Driving and L… •

DTC codes / P00xx · Fuel and air metering and auxiliary emission controls / P008F

P008FEngine Coolant Temperature/Fuel Temperature Correlation

P008F indicates that the powertrain control module (PCM) has detected an implausible relationship between the engine coolant temperature (ECT) sensor and the fuel temperature sensor during cold starts or specific operating conditions. The PCM expects the fuel temperature to rise in a predictable manner relative to coolant temperature, and when the two signals deviate beyond calibrated limits, this code is set.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) with often no other noticeable symptoms.
  • Rough idle or hesitation during cold engine operation.
  • Reduced fuel economy or poor performance under load.
  • Hard starting or extended cranking when the engine is cold.
  • In rare cases, the engine may enter limp mode or exhibit reduced power.
  • No drivability issues at all, with the code being the only indication of a problem.

Common causes, most likely first

  1. Faulty fuel temperature sensor or its wiring connector.
  2. Faulty engine coolant temperature (ECT) sensor or its circuit.
  3. Corroded, chafed, or open wiring in the sensor circuits.
  4. Poor electrical connection at the PCM or sensor grounds.
  5. Sticking or failed thermostat causing abnormal coolant temperature behavior.
  6. Low fuel level or fuel system issues affecting fuel temperature readings.
  7. PCM software calibration issue or internal PCM fault (less common).

How to diagnose and fix it

  1. Connect a scan tool and record freeze-frame data for both ECT and fuel temperature sensors to see the actual values when the code set.
  2. Visually inspect the fuel temperature sensor and ECT sensor connectors and wiring for damage, corrosion, or loose pins.
  3. Measure the resistance of both sensors with a multimeter and compare to manufacturer specifications across temperature ranges.
  4. Check the thermostat operation and coolant level to rule out cooling system faults that could skew ECT readings.
  5. Perform a voltage drop test on the sensor ground and signal circuits to ensure integrity under load.
  6. If sensor values are within spec but the code persists, check for technical service bulletins (TSBs) or PCM software updates.
  7. Replace the faulty sensor or repair wiring as needed, clear the code, and verify the repair by monitoring live data during a cold start.

What most technicians overlook with P008F

  • A marginal thermostat that opens slightly early or late can cause the ECT signal to fall outside the expected correlation window without setting a thermostat-specific code.
  • Fuel temperature sensor readings are often ignored during routine diagnostics, but they can drift gradually and only trigger P008F under specific cold-start conditions.
  • Wiring harness damage near the fuel tank or along the frame rail is a common hidden cause, especially on vehicles with prior underbody repairs.
  • The code can be set by a weak battery or charging system issue that causes voltage spikes affecting sensor signals during cranking.
  • Replacing both sensors without verifying the circuits is a costly misdiagnosis; always check resistance and voltage drop first.

Can I keep driving with P008F?

The vehicle is generally safe to drive with P008F because it rarely causes immediate drivability problems, but you should avoid extended driving until the cause is diagnosed to prevent potential fuel economy loss or unnoticed sensor failure. Schedule a diagnostic inspection at your earliest convenience.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage