P0091Fuel Pressure Regulator A 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
- On common-rail diesel and gasoline direct-injection engines, a high-pressure pump feeds the fuel rail, a sensor measures rail pressure, and the engine control module regulates it towards a target from its maps. The fuel pressure regulator A is the actuator the manufacturer designates for this: depending on the system a pressure control valve that releases fuel from the rail, or the control valve on the high-pressure pump. Some manufacturers report the pump valve under the "fuel volume regulator" codes instead. P0091 means the voltage in the control circuit is too low, typically a short to ground. Rail pressure can then no longer be controlled as intended, and the engine usually runs in reduced power.
- What you may notice
- Check engine light on
- Reduced power mode
- Hard starting or stalling
- Likely causes
- LikelyControl wire shorted to ground, or connector corroded
- LikelyRegulator coil faulty
- PossibleFuse or supply voltage 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 · Often possible to do yourself.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.