P009C Fuel Pressure Relief Control Circuit Low

The fuel pressure relief control is an electrically controlled valve on the fuel rail that the engine control module opens to reduce rail pressure deliberately, for example on overrun, on load drops or when the engine is switched off. It differs from the purely mechanical pressure relief valve, which opens passively at overpressure, and from the pressure regulator, which controls pressure continuously. Manufacturer documents show this code mainly on heavy-duty diesel engines. P009C reports too low a voltage in the control circuit, typically a short to ground. Rail pressure can then not be reduced as intended, and the engine may be derated.

Likely causes

Symptoms

• Check engine light on
• Reduced power (derate) possible

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov, de.wikipedia.org.