P008F: Engine Coolant Temperature/Fuel Temperature Correlation

What it means

The control module detects that engine coolant temperature and fuel temperature readings do not correlate as expected.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The control module reads engine coolant temperature and fuel temperature to check whether the two readings are plausible in relation to operating conditions. P008F sets when those temperatures do not correlate as expected, which can result from either sensor or its wiring rather than an actual overheating condition.

Common causes

Most likely first.

1. Engine coolant temperature sensor reading inaccurate
2. Fuel temperature sensor reading inaccurate
3. Wiring or connector fault affecting either sensor

Symptoms

• Check engine light on
• Temperature gauge may read unusually or fluctuate
• Hard starting or reduced performance

How to diagnose it

1. Save freeze-frame data and compare coolant and fuel temperature readings in live data after a cold soak; they should be plausible for the same surrounding conditions.
2. Check whether the dashboard temperature gauge agrees with the scan-tool coolant temperature reading as the engine warms.
3. Inspect both the coolant temperature sensor and fuel temperature sensor connectors and wiring for corrosion, loose pins, damage, or chafing.
4. Check each sensor's readings as temperature changes and compare its response with the manufacturer's specification.
5. Test the wiring and connector circuits for opens, shorts, or poor grounds before replacing either sensor.

Common fixes

• Repair a loose, damaged, or corroded sensor connector or wiring.
• Replace the coolant temperature sensor if its reading is inaccurate in testing.
• Replace the fuel temperature sensor if its reading is inaccurate in testing.
• Repair a circuit fault affecting the shared supply or ground, if confirmed by testing.

Can I keep driving?

If the gauge indicates overheating, stop safely and let the engine cool; do not rely on this code to rule out a real cooling problem. If temperature indications are normal but starting or performance is affected, limit driving until the sensor readings are checked.