P008D

Fuel Cooler Pump Control Circuit Low

P008D is a generic OBD-II powertrain diagnostic trouble code: Fuel Cooler Pump Control Circuit Low. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P008D
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P008D means

Code P008D is stored when the Powertrain Control Module (PCM) detects an abnormally low voltage signal on the fuel cooler pump control circuit. The fuel cooler pump is a feature found primarily on diesel-powered vehicles — it circulates engine coolant through a heat exchanger to lower the temperature of excess fuel returning to the fuel tank. Hot return fuel degrades injector seals, accelerates pump wear, and can cause vapour lock or pressure instability in the high-pressure rail. When the PCM commands the pump on and the feedback voltage drops below the expected threshold, it logs P008D and illuminates the MIL. Left unaddressed, chronically overheated return fuel accelerates wear on fuel system components and can indirectly stress internal engine parts. The fault is most commonly seen on Ford Power Stroke, GM Duramax, and Dodge Cummins diesel platforms, though it also appears on certain BMW and Volkswagen diesel applications equipped with active fuel cooling loops.

Common causes

Most-frequently reported root causes when P008D is logged.

  • 1
    Defective or seized fuel cooler pump motor drawing excessive current, pulling the control signal low
  • 2
    Open circuit or broken wire in the pump control harness between the PCM and pump
  • 3
    Corroded, damaged, or backed-out connector pins at the pump or PCM connector
  • 4
    Blown fuse or failed relay supplying power to the fuel cooler pump circuit
  • 5
    Short to ground on the pump control or power supply wire
  • 6
    Faulty PCM output driver for the fuel cooler pump channel
  • 7
    High resistance in the circuit ground path causing false low-voltage reading

Symptoms drivers notice

Check Engine Light (MIL) illuminated
Increased fuel temperatures, potentially triggering additional fuel-temperature-related DTCs
Reduced engine performance or power output under sustained high-load conditions
Increased fuel consumption due to hot, less-dense return fuel
Audible squealing or grinding noise from a failing fuel cooler pump
Possible fuel odour from overheated return fuel

How to diagnose P008D

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record freeze-frame data, and note any accompanying fuel temperature or pressure DTCs that may indicate the root cause
  2. 2
    Perform a thorough visual inspection of the fuel cooler pump wiring harness, connectors, and pump body — look for chafed insulation, burn marks, corrosion, or coolant contamination
  3. 3
    Check the fuse and relay associated with the fuel cooler pump circuit; replace any blown fuse and retest to confirm the circuit is not shorted
  4. 4
    With the ignition on and engine off, backprobe the control wire at the PCM connector using a digital multimeter — confirm the PCM is commanding the correct voltage when the pump should be active
  5. 5
    Measure voltage at the pump connector with the ignition on; low or absent voltage points to a wiring or relay fault, while correct voltage with no pump operation points to a failed pump
  6. 6
    Perform a continuity and resistance check on the pump control circuit from PCM pin to pump connector; resistance above 0.5 Ω indicates a wiring fault
  7. 7
    If wiring checks pass, replace the fuel cooler pump and retest; clear the DTC and verify the code does not return after a full drive cycle

Related powertrain codes

Frequently asked questions

Is it safe to drive with a P008D code active?

Short trips are generally tolerable, but prolonged high-load driving will cause fuel temperatures to climb, accelerating wear on injectors, the high-pressure pump, and other fuel system components. Repair is recommended promptly.

Which vehicles most commonly show P008D?

The code is predominantly seen on diesel-powered trucks and SUVs — Ford 6.4L and 6.7L Power Stroke, GM 6.6L Duramax, and Dodge/Ram 6.7L Cummins — as well as some European diesel passenger cars with active fuel cooling.

Can a P008D be caused by a blown fuse alone?

Yes. A blown pump fuse removes power from the circuit, causing the PCM to read a low or absent voltage on its feedback line and log P008D. Always check fuses and relays before condemning the pump or PCM.

Will clearing the code fix the problem?

No. Clearing the code without repairing the underlying electrical or mechanical fault will cause it to return within one or two drive cycles once the PCM re-evaluates the pump circuit.

Disabling P008D in software

RaceTune can permanently disable P008D — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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