Open P008C Fuel Cooler Pump Control Circuit

What is the P008C Code?

The P008C trouble code is a generic powertrain code that indicates an open circuit in the fuel cooler pump. This code primarily affects diesel vehicles equipped with OBD-II standards, including Ford/Powerstroke, BMW, Dodge/Ram/Cummins, Chevrolet, and GMC models. Although generic, specific diagnostic procedures may vary by manufacturer.

Fuel Cooler Pump Circuit Operation

In a diesel engine, the fuel cooler’s role is to lower the temperature of excess diesel fuel before it returns to the tank. Functioning like a small radiator, it uses the engine’s coolant to dissipate heat. The fuel cooler pump, controlled by the PCM (Powertrain Control Module), circulates the fuel through this circuit. A malfunction (open circuit) disrupts this process, which can lead to fuel overheating and eventually damage the injection system or the engine.

Other related codes may appear, such as P008D and P008E.

Severity Level and Symptoms

The severity of the P008C code is moderate to high. A prolonged fault can cause premature injector wear and a significant drop in performance.

Common Symptoms:

• Reduced performance and sluggish acceleration
• Unstable or irregular idle
• Check engine light illuminated
• Abnormally high fuel consumption
• Abnormal noises (grinding, clicking) from the pump

Possible Causes of the Fault

• Faulty fuel cooler pump
• Corroded, oxidized, or damaged electrical connector
• Cut, chafed, or short-circuited wiring
• Internal PCM module failure

Diagnostic Procedure

1. Visual Inspection

Locate the pump, cooler, and PCM module. Thoroughly inspect all associated connectors and wiring for signs of corrosion, burning, damaged insulation, or exposed wires. Also, check the condition and level of the coolant.

2. Electrical Checks (Advanced)

Using a digital multimeter and manufacturer technical data (wiring diagrams, voltage ranges):

• Check for power and ground at the pump.
• Perform a continuity test on the wires (with power off). A healthy circuit should show 0 Ω resistance.
• Correct voltage with an inactive pump most likely indicates a faulty pump.

Tip: Consult your vehicle’s Technical Service Bulletins (TSBs) to check for any known issues and official correction procedures.

Common Repairs

• Replacement of the fuel cooler pump
• Cleaning of terminals and electrical connectors
• Repair or replacement of damaged wiring harness
• Replacement or reprogramming (“flash”) of the PCM module

Have questions about diagnosing the P008C code on your vehicle? Consult a diesel specialist or share your experience in the comments below!