P008C: Fuel Cooler Pump Control Circuit Open
May cause reduced engine performance, increased fuel consumption and potential fuel system issues if not addressed
Overview
P008C indicates an open circuit in the fuel cooler pump control circuit, detected by the Powertrain Control Module on vehicles with a fuel cooling system, often diesel engines. Investigate fuel cooler pump, wiring, connectors, fuses/relays, and PCM outputs.
Common Symptoms
- Check Engine Light illuminated
- Decreased engine performance or power loss
- Acceleration and idle irregularities
- Increased fuel consumption
- Unusual noise from fuel cooler pump
Most Common Causes
Pump internal failure or inability to run due to open circuit within pump winding or internals.
Open circuit often due to harness damage, corrosion, broken terminals or connector issues.
Electrical supply to pump interrupted by protective device failure.
Rare, but possible internal PCM output driver failure causing open circuit detection.
Diagnostic Steps
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Verify the presence of the P008C code with a professional OBD-II scan tool and check for related codesExpected: P008C present; potential related fuel system or circuit codesInterpretation: Confirms the code and checks for additional context.
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Perform a thorough visual inspection of the fuel cooler pump, wiring harness, and connectorsExpected: No visible damage, corrosion, broken wires or loose connectorsInterpretation: Identifies obvious physical issues that would cause an open circuit.
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Check fuses and relays associated with the fuel cooler pump circuitExpected: Fuses intact and relay clicks/operates properlyInterpretation: Determines whether power supply disruption is cause.
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Use a multimeter to test for voltage at the fuel cooler pump control circuit and continuity of wiringExpected: Correct voltage present and continuity within expected rangeInterpretation: Validates electrical integrity of circuit; opens or abnormal readings indicate wiring/pump issues.
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Test the fuel cooler pump operation directly if accessible and verify PCM output signalsExpected: Pump receives control signal and operates when commandedInterpretation: Confirms pump and PCM driver functionality.
Repair Solutions
Costs vary widely depending on vehicle and diesel engine application; includes parts and labor.
Depends on extent of harness damage and accessibility.
Simple electrical component replacements; ensure root cause of failure is addressed.
High cost and should be last resort after all wiring and component tests.
Common Misdiagnoses
Avoid these common diagnostic mistakes:
- Assuming poor fuel quality or clogged fuel filter is the cause without electrical diagnostics
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