Fuel and air

P008D — Fuel Cooler Pump Control Circuit Low

Severity: medium Drive with care, to a shop

What P008D means

The fuel cooler pump circulates coolant through a heat exchanger to keep fuel temperature down, most often on diesel engines. The engine control module drives the pump and watches the control circuit. P008D sets when the circuit voltage is lower than expected, due to an open circuit, a short to ground, or a failed pump.

Symptoms

  • Check Engine light on
  • Reduced engine power
  • Surging during acceleration or at idle
  • Higher fuel consumption
  • Unusual noise near the fuel cooler pump

Possible causes

  1. Failed or seized fuel cooler pump
  2. Damaged or corroded wiring and connectors in the pump control circuit
  3. Bad pump relay or blown fuse
  4. Rarely, a faulty ECM/PCM driver

How to diagnose

  1. Scan for codes and freeze-frame data, and look for other fuel or cooling codes
  2. Inspect the pump fuse and relay, and swap the relay with a known good one
  3. Inspect the harness and pump connector for chafing, corrosion and heat damage
  4. Check for power and ground at the pump connector with a multimeter
  5. Test the control wire for continuity to the ECM and for a short to ground
  6. Command the pump on with a scan tool and see if it runs
  7. If wiring tests good and the pump does not respond, replace the pump; suspect the ECM last

Common fixes

  • Replace the faulty fuel cooler pump
  • Repair wiring and replace damaged connectors
  • Replace the relay or fuse
  • Replace or reprogram the ECM/PCM if confirmed faulty

Questions and answers

What does P008D mean?

It means the control module sees low voltage in the fuel cooler pump control circuit. The cause is usually the pump, its wiring, or the relay.

Can I drive with P008D?

Briefly, yes, but avoid heavy loads. Delaying the repair risks overheated fuel and loss of power.

Where do I start diagnosing P008D?

Check the fuse, relay and pump connector first, then test for power and ground at the connector. Wiring and the pump itself are the most common culprits.

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.