P0001Fuel Volume Regulator A Control Circuit/Open
- 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. P0001 is set when the control module detects that the control circuit of this valve is open, i.e. no plausible current flows when the valve is driven. Rail pressure can then no longer be controlled as intended. Whether the valve is open or closed without current depends on the design, so the same fault can cause excess pressure in one system and no pressure in another.
- What you may notice
- Check engine light on
- Engine cranks but does not start, or stalls (normally closed valve)
- Loss of power or limp mode (normally open valve)
- Additional rail pressure codes possible
- Likely causes
- LikelyConnector at the regulator loose, corroded or unplugged
- PossibleSolenoid coil of the regulator open
- PossibleBroken wire in the harness, e.g. chafing or rodent damage
- 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.