Fuel and air

P008C — Fuel Cooler Pump Control Circuit Open

Severity: medium Drive with care, to a shop

What P008C means

The engine control module runs an electric pump that circulates coolant through a fuel cooler. The cooler lowers the temperature of fuel returning to the tank, which matters most on diesel engines. P008C sets when the module sees an open circuit in the pump control line, meaning it commands the pump but does not get the expected electrical response.

Symptoms

  • Check Engine light on
  • Reduced power
  • Rough idle or hesitation on acceleration
  • Higher fuel consumption
  • Unusual noise from the pump, or no pump sound at all
  • Hot fuel in the return line or tank

Possible causes

  1. Failed fuel cooler pump (open winding)
  2. Damaged or corroded wiring or connectors in the pump circuit
  3. Blown fuse
  4. Faulty pump relay
  5. Open control wire or lost ground
  6. Failed driver circuit inside the PCM (rare)

How to diagnose

  1. Scan for all codes and freeze frame data, clear the code and see if it returns.
  2. Inspect the pump harness and connectors for chafing, heat damage and corrosion.
  3. Check the fuse and relay for the pump circuit; swap in a known good relay if needed.
  4. Command the pump on with a scan tool active test, if supported, and listen for it running.
  5. Check for power and ground at the pump connector with a multimeter.
  6. Test the control wire from the PCM to the pump for opens and shorts.
  7. Measure the pump's winding resistance and compare it with the manufacturer's spec.
  8. If everything checks out, verify the PCM output signal before suspecting the module.

Common fixes

  • Replace the blown fuse or faulty relay
  • Repair damaged wiring and clean or replace the connector
  • Replace the fuel cooler pump
  • Repair or replace the PCM if an internal driver fault is confirmed

Questions and answers

What does P008C mean?

It means an open circuit in the fuel cooler pump control line. The PCM does not see normal operation, most often due to the pump, wiring, a fuse or a relay.

Can I drive with P008C?

For a short time, with care. Overheated fuel can harm the fuel system and reduce power, so get it diagnosed soon.

What should I check first?

The fuse, relay and pump connector. These are quick, cheap checks that often find the cause before you need to replace the pump.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.