P0004Fuel Volume Regulator A Control Circuit High
- 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 volume regulator (also called metering unit or suction control valve) is a solenoid valve on the inlet side of the high-pressure pump, used mainly on common-rail diesel engines. The engine control module pulses it to set how much fuel the pump draws in and delivers to the rail, and in this way controls rail pressure. P0004 means the voltage on the control circuit stays too high for the commanded duty cycle, typically because of a short to battery voltage, or, with a switched ground side, an open circuit. The valve can then not be energised; a normally open design delivers maximum fuel and rail pressure rises.
- What you may notice
- Check engine light on
- Loss of power or limp mode
- Rough running or diesel knock possible
- Excess rail pressure codes possible
- Likely causes
- LikelyShort to battery voltage in the harness
- PossibleOpen coil or wire, reported as high with ground-side switching
- PossibleConnector fault at the regulator
- 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 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.