P008C
Fuel Cooler Pump Control Circuit OpenP008C is a generic OBD-II powertrain diagnostic trouble code: Fuel Cooler Pump Control Circuit Open. 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.
What P008C means
P008C is set when the ECM or PCM detects an open circuit in the electrical control circuit for the fuel cooler pump. The fuel cooler pump — found primarily on diesel engines such as Ford 6.4L Power Stroke, BMW diesel, Ram/Cummins, and certain GM Duramax applications — circulates engine coolant through a small fuel cooler (heat exchanger) to lower the temperature of high-pressure fuel returning from the injector rails back to the fuel tank. Hot return fuel accelerates injector seal degradation, reduces fuel density, and in extreme cases can cause vapour-lock-like fuelling irregularities. An open circuit means the ECM cannot energise the pump: the control wire may be broken, a connector unplugged or corroded, a fuse blown, or the pump relay/pump itself has failed internally. In many cases the code presents with no dramatic drivability symptoms beyond the MIL, but sustained elevated fuel temperatures will progressively stress injectors and fuel system seals, making timely repair important. The code is particularly prevalent on Ford 6.4L Power Stroke trucks from 2008–2010.
Common causes
Most-frequently reported root causes when P008C is logged.
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1
Open (broken) conductor in the fuel cooler pump control wire between the PCM and pump connector
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2
Corroded, damaged, or disconnected connector at the fuel cooler pump leaving the circuit open
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3
Blown fuse in the fuel cooler pump control or supply circuit
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4
Failed fuel cooler pump motor with an open internal winding preventing current draw
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5
Faulty pump relay that does not close, preventing power from reaching the pump
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6
Damaged wiring harness from chafing, rodent damage, or previous repair work
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7
PCM/ECM internal fault affecting the fuel cooler pump driver output (rare)
Symptoms drivers notice
How to diagnose P008C
A typical diagnostic flow when this code is present.
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1
Scan for all stored codes; check for related fuel temperature or fuel pressure codes that indicate elevated fuel temps are already occurring
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2
Locate and inspect all fuses associated with the fuel cooler pump circuit; replace any blown fuse and investigate the root cause before re-testing
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3
Perform a thorough visual inspection of the fuel cooler pump, its connector, and the wiring harness for obvious damage, disconnection, or corrosion
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4
With the ignition on, measure supply voltage at the pump connector; absent voltage points to a fuse, relay, or wiring fault upstream
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5
Test continuity of the control and ground wires between the PCM connector and pump connector; infinite resistance (OL) confirms an open conductor
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6
Check pump relay operation by swapping with an identical relay or testing relay coil and contact resistance
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7
If wiring and relay test normal, measure pump motor resistance at the pump terminals; an open reading indicates a failed pump requiring replacement
Related powertrain codes
Frequently asked questions
Is P008C a serious fault?
It is not immediately dangerous, but it should not be ignored. Without the fuel cooler pump operating, fuel temperatures in high-demand driving conditions will rise, accelerating wear on injector seals, O-rings, and fuel lines. It is a moderate-priority repair.
Which vehicles most commonly get P008C?
P008C is most commonly seen on Ford 6.4L Power Stroke diesel trucks (2008–2010), but also appears on other diesel platforms from BMW, Ram/Cummins, and GM that use a dedicated fuel cooler pump in the return circuit.
Can a blown fuse cause P008C?
Yes. A blown fuse in the fuel cooler pump supply or control circuit creates an open condition that the PCM interprets as a circuit open fault. Always check fuses first — they are the simplest and cheapest fix, but the underlying reason the fuse blew should also be investigated.
Will the engine go into limp mode with P008C?
Typically no. Most vehicles with P008C illuminate the MIL and continue operating normally. Limp mode is not usually triggered unless additional fuel system or temperature codes accompany this fault. However, some calibrations on specific diesel platforms may apply slight power reduction as a precaution.
Disabling P008C in software
RaceTune can permanently disable P008C — 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.
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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