P008D: Fuel Cooler Pump Control Circuit Low

On some common-rail diesels, fuel returning from the injection system is cooled in a heat exchanger connected to a low-temperature coolant circuit. An electric coolant pump, switched by the engine control module depending on fuel temperature, drives this circuit. P008D reports too low a voltage, typically a short to ground of this pump or its relay. If the pump fails for long, the fuel runs hotter; some systems then limit power to protect components.

Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

Symptoms

Check engine light on
Often no further symptoms
Reduced power when fuel gets hot possible

Most likely causes

Connector or wiring faulty
Fuel cooler pump faulty
Relay or fuse faulty
Output driver in the engine control module faulty

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring
With the connector unplugged, check whether the signal wire is making contact with ground.
Use live data to compare the reading with actual conditions
Measure power, ground, and signal
Replace the sensor if the circuit is good

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P008D means

P: Powertrain: engine and transmission
0: Generic code: same on every make
0: Subsystem depends on the code range
8D: Specific fault in that system

Frequently asked questions

Can I keep driving with code P008D?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P008D?

The most common causes are: connector or wiring faulty; fuel cooler pump faulty; relay or fuse faulty.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.