P008E: Fuel Cooler Pump Control Circuit High
Check Engine Light illumination, potential reduced performance under heavy load and possible fuel system heating issues
Overview
P008E indicates a high voltage condition in the fuel cooler pump control circuit, common on diesel vehicles with fuel cooling systems; involves electrical faults in wiring, connectors, pump, or PCM
Common Symptoms
- Check Engine Light (MIL/CEL) illuminated
- Decreased engine performance or surging under load
- Increased fuel consumption
- Noise from the fuel cooler pump
- Possible hard starting under high temperature conditions
Most Common Causes
Pump internal electrical failure can manifest as high voltage signal to PCM
Most frequent cause is electrical faults in circuit conductors or connectors
High resistance ground can simulate high voltage condition
Rare, but control unit failure or software error might cause misreporting
Diagnostic Steps
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Confirm P008E and related codes with professional scan toolExpected: P008E present; note any other fuel system or electrical codesInterpretation: Ensures correct focus on fuel cooler circuit issues
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Perform visual inspection of fuel cooler pump wiring and connectorsExpected: No corrosion, chafing, broken wires or burnt spotsInterpretation: Defects here often cause voltage anomalies
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Measure voltage at pump connector with digital multimeterExpected: Voltage within OEM specificationInterpretation: Out-of-spec voltage confirms circuit or pump problem
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Test resistance of the fuel cooler pump (disconnected)Expected: Resistance within expected rangeInterpretation: Open or shorted windings indicate pump failure
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Check ground circuit continuity to chassisExpected: Low resistance to groundInterpretation: High resistance suggests poor ground contributing to high voltage reading
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Verify PCM output signal and reference voltage (last resort)Expected: Proper control signal waveform and levelInterpretation: Abnormal PCM output may require reflashing or replacement
Repair Solutions
Fixing electrical faults is often the most cost-effective solution
Cost varies widely by vehicle make/model and accessibility
Often overlooked but can resolve high voltage readings
Only after verifying all wiring and component integrity
Common Misdiagnoses
Avoid these common diagnostic mistakes:
- Assuming high fuel temperature issue is engine overheating instead of fuel cooling circuit fault
- Replacing fuel filter instead of inspecting wiring and connectors
- Failing to check ground integrity
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