P008C - Fuel Cooler Pump Control Circuit / Open
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P008C is a diagnostic trouble code (DTC) for 'Fuel Cooler Pump Control Circuit / Open'. This means the Engine Control Module (ECM) has detected that the electrical circuit controlling the fuel cooler pump is incomplete or broken. Fuel coolers are used primarily in common-rail diesel engines to reduce the temperature of the fuel returning to the tank, ensuring fuel stability and protecting plastic tank components. The ECM monitors the circuit integrity; an 'Open' condition implies a lack of continuity, such as a blown fuse, a broken wire, or a failed pump motor winding.
Possible Causes
Faulty fuel cooler pump (internal open circuit in the motor)
Damaged wiring harness or corrosion in the pump connectors
Blown fuse for the fuel cooling system
Defective fuel cooler control relay or internal ECU fault
Symptoms
Recommended Solution
- Visual Inspection: Check the wiring harness to the fuel cooler pump for chafing, heat damage, or corroded pins in the connector.
- Fuse Check: Inspect the fuse dedicated to the fuel cooling system in the power distribution center.
- Resistance Measurement: Disconnect the pump and measure resistance across the pump terminals. A reading of infinity indicates an internal open circuit.
- Voltage Drop Test: Verify 12V is present at the connector when the ECM commands the pump ON using a bi-directional scan tool.
- Component Test: Perform a functional test using the diagnostic software to command the pump and verify operation.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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