Engine Coolant Temp/Fuel Temp Correlation Issue
The P008F code indicates that the Engine Control Module (ECM) has detected a discrepancy between the engine coolant temperature (ECT) sensor and the fuel temperature sensor readings. This typically occurs when the sensors provide conflicting data, such as the coolant temperature being too high while the fuel temperature is too low, or vice versa. The ECM uses these inputs for fuel injection timing and mixture control, so a correlation fault can lead to poor engine performance, increased emissions, and potential drivability issues.
1. Most Common Causes
- Faulty engine coolant temperature (ECT) sensor or signal drift
- Faulty fuel temperature sensor (FTS) or signal drift
- Short to ground, open circuit, or high resistance in ECT or FTS wiring or connectors
- Thermostat stuck open (engine fails to reach normal operating temperature, affecting logical correlation)
- Coolant leak or low coolant level (air pockets around ECT sensor)
- Faulty PCM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation
- Hard starting, especially when cold
- Engine overheating or running too cool
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect ECT and fuel temperature sensor connectors and wiring for damage or corrosion.
Step 3: Compare ECT and fuel temperature sensor readings using a scan tool; they should be similar when engine is cold.
Step 4: Test sensor resistance and voltage according to manufacturer specifications.
Step 5: Check coolant level and condition; verify thermostat operation.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the engine may run poorly, overheat, or cause further damage. Short trips to a repair shop are acceptable if symptoms are mild.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150, including parts and labor, depending on which sensor needs replacement and labor rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.