P008F

Engine Coolant Temperature/Fuel Temperature Correlation

P008F is a generic OBD-II powertrain diagnostic trouble code: Engine Coolant Temperature/Fuel Temperature Correlation. It is logged by the engine control unit when the coolant monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P008F
Group
Powertrain
System
Coolant
Severity
Warning (MIL on)
Need P008F disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P008F means

Code P008F is stored when the PCM detects a significant discrepancy between the Engine Coolant Temperature (ECT) sensor signal and the Fuel Temperature (FT) sensor signal. Both sensors use similar negative-temperature-coefficient (NTC) thermistor technology, and when the engine has been sitting overnight and is fully cold-soaked, both readings should be within a few degrees of each other and of ambient temperature. The PCM exploits this cold-soak window to cross-check sensor calibration: if the two readings diverge beyond a manufacturer-defined threshold — typically 10–15 °C — the module concludes that one or both sensors have drifted out of calibration or have failed. The code can also be triggered when the engine is hot if the fuel temperature sensor reads an implausibly low value compared to a hot ECT. Consequences include incorrect fuelling corrections, poor cold-start management, increased emissions, and potential catalytic converter stress from a persistently rich or lean mixture driven by an erroneous temperature input.

Common causes

Most-frequently reported root causes when P008F is logged.

  • 1
    Faulty Engine Coolant Temperature (ECT) sensor with drifted calibration or complete failure
  • 2
    Defective Fuel Temperature (FT) sensor producing out-of-range or stuck voltage
  • 3
    Open circuit, short to ground, or short to voltage on either sensor signal wire
  • 4
    Corroded or loose connectors at the ECT or FT sensor causing intermittent signal loss
  • 5
    Coolant system issue (low coolant level, thermostat stuck open) causing ECT to read abnormally low
  • 6
    Fuel system contamination or aeration causing abnormal fuel temperature readings
  • 7
    PCM internal fault or software calibration error causing incorrect sensor comparison thresholds

Symptoms drivers notice

Check Engine Light (MIL) illuminated
Reduced engine performance and sluggish throttle response
Poor fuel economy due to incorrect fuelling corrections based on faulty temperature data
Excessive exhaust smoke (black or white) from an over-rich or improper mixture
Difficult cold starts if the ECT sensor is sending incorrect data to the cold-start enrichment routine
Potential catalytic converter damage from prolonged exposure to an incorrect air-fuel ratio

How to diagnose P008F

A typical diagnostic flow when this code is present.

  1. 1
    Allow the engine to fully cold-soak (minimum 3 hours); connect a scan tool and compare live ECT and fuel temperature readings — both should be within 5–10 °C of each other and ambient temperature at cold soak
  2. 2
    Visually inspect wiring and connectors for both the ECT and fuel temperature sensors, looking for corrosion, damaged terminals, or chafed insulation
  3. 3
    Unplug each sensor individually and measure its resistance with a DVOM, comparing against the manufacturer's temperature-resistance chart; a sensor that reads open, short, or significantly out of specification should be replaced
  4. 4
    Verify reference voltage (nominally 5 V) and a clean ground are present at both sensor connectors with the ignition on
  5. 5
    Use an infrared thermometer or thermal probe to compare actual coolant and fuel temperatures against scanner readings to pinpoint which sensor is erroneous
  6. 6
    Check coolant level and thermostat operation; a stuck-open thermostat can cause ECT to read abnormally low, mimicking a sensor fault
  7. 7
    Clear the DTC, perform a complete drive cycle including a cold start, and confirm the code does not return; if it persists with all sensors and wiring verified good, check for available PCM software updates

Related powertrain codes

Frequently asked questions

Why do the ECT and fuel temperature sensors need to match?

The PCM uses the cold-soak window — when both the engine and fuel have equilibrated to ambient temperature — to cross-validate that neither sensor has drifted. If they disagree significantly when both should read ambient, the PCM flags a calibration fault.

How do I know which sensor is faulty — ECT or fuel temperature?

After a full cold soak, compare both readings to actual ambient temperature using an independent thermometer or thermal probe. The sensor reading furthest from ambient is the likely culprit. You can also compare sensor resistance against manufacturer specifications.

Can low coolant level cause P008F?

Yes. If the coolant level is too low to fully immerse the ECT sensor, the sensor may read lower than the actual coolant temperature, creating a false correlation error. Always check coolant level before replacing sensors.

Is P008F specific to diesel engines?

No. P008F appears on both gasoline and diesel engines equipped with a separate fuel temperature sensor. It is more common on diesels because fuel temperature management is more critical in high-pressure common-rail systems, but the code is generic SAE and can appear on any OBD-II vehicle with a fuel temperature sensor.

Disabling P008F in software

RaceTune can permanently disable P008F — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECU families we can disable P008F on

We hold the DaVinci A2L disable definitions for these families, so the exact P008F path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch EDC17C50 verified
  • Bosch EDC17C56 verified
  • Bosch MD1CP002 verified
  • Bosch MD1CS001 verified

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

Got P008F in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file