P009CFuel Pressure Relief Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light on
- Reduced power (derate) possible
- Likely causes
- LikelyWiring chafed with short to ground, or connector corroded
- PossibleValve coil faulty
- RareOutput driver in the engine control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.