Faulty or drifting engine coolant temperature sensor giving an inaccurate reading; Faulty or drifting fuel temperature sensor, which may be built into the fuel pump, rail or filter housing depending on the engine; Damaged wiring, corroded terminals or poor connector contact on either sensor circuit, causing resistance or an offset reading; Thermostat stuck open, so the engine runs cooler than expected and coolant temperature does not match fuel temperature; Low coolant level or air in the cooling system causing a false coolant temperature reading; Test run too soon after the engine was last running, so the temperatures had not equalised and a fault was falsely flagged; Engine control unit fault or a software issue affecting the correlation test.

P008F

Engine Coolant Temperature/Fuel Temperature Correlation.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
8F: FaultThe specific fault in that area

What it means

P008F is the generic SAE J2012 code for an Engine Coolant Temperature/Fuel Temperature Correlation fault. The engine control unit compares the engine coolant temperature sensor reading with the fuel temperature sensor reading, usually after a long soak with the engine off when the two should be close. If the two differ by more than the expected amount, it sets the code. Which sensors and conditions are used depends on the model and engine.

Symptoms

Engine warning light on
Hard or extended cranking when starting, especially from cold
Rough idle or poor running until warmed up
Cooling fan running at odd times or not as expected
Poor fuel economy or reduced performance
Temperature gauge reading incorrectly

Possible causes

Faulty or drifting engine coolant temperature sensor giving an inaccurate readinglikely
Faulty or drifting fuel temperature sensor, which may be built into the fuel pump, rail or filter housing depending on the enginelikely
Damaged wiring, corroded terminals or poor connector contact on either sensor circuit, causing resistance or an offset readinglikely
Thermostat stuck open, so the engine runs cooler than expected and coolant temperature does not match fuel temperaturepossible
Low coolant level or air in the cooling system causing a false coolant temperature readingpossible
Test run too soon after the engine was last running, so the temperatures had not equalised and a fault was falsely flaggedpossible
Engine control unit fault or a software issue affecting the correlation testrare

How to diagnose

Read the stored and pending codes and freeze frame data, noting engine temperatures, soak time and any other temperature or sensor codes
Check coolant level and condition, and look for leaks or signs of air in the system
Inspect the wiring and connectors of the coolant and fuel temperature sensors for damage, corrosion, water ingress or poor pin tension
With the engine fully cold after a long soak, compare live coolant temperature, fuel temperature and intake air temperature; they should be close to each other and to ambient
Warm the engine and watch the coolant temperature rise smoothly to the thermostat opening point, checking for a thermostat that opens early
Measure the resistance of each sensor against the manufacturer's temperature specification and check the sensor supply and signal circuits for continuity and shorts
Check for technical service bulletins or software updates relevant to the vehicle model and engine
Clear the code and retest after a full cold soak to see whether it returns

How to fix

Replace the coolant temperature sensor if its readings are out of specification
Replace the fuel temperature sensor or the assembly it is part of, following the manufacturer's procedure for the engine
Repair or replace damaged wiring and clean or renew faulty connectors
Replace a thermostat that is stuck open and refill and bleed the cooling system correctly
Top up or refill coolant and bleed air from the system
Update the engine control unit software only if an outdated calibration is a known cause for that model, or repair or replace the unit if it is confirmed faulty

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but get it checked soon, as incorrect temperature readings can affect starting, fuelling and cooling fan control. Stop and investigate if the temperature gauge rises abnormally or the engine overheats.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.