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.
Medium severity. Can I keep driving?Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.
Symptoms
- 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
Most likely causes
- Connector at the regulator loose, corroded or unplugged
- Solenoid coil of the regulator open
- Broken wire in the harness, e.g. chafing or rodent damage
- Output driver in the engine control module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P0001 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 0: Subsystem depends on the code range
- 01: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0001?
Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.
What causes code P0001?
The most common causes are: connector at the regulator loose, corroded or unplugged; solenoid coil of the regulator open; broken wire in the harness, e.g. chafing or rodent damage.
Related codes
- P0002Fuel Volume Regulator A Control Circuit Range/Performance
- P0003Fuel Volume Regulator A Control Circuit Low
- P0004Fuel Volume Regulator A Control Circuit High
- P000EFuel Volume Regulator Control Exceeded Learning Limit
- P000FFuel System Over Pressure Relief Valve Activated
- P0087Fuel Rail/System Pressure - Too Low
- P0088Fuel Rail/System Pressure - Too High
- P2370Fuel Volume Regulator B Control Circuit/Open
Sources
- law.cornell.edu: 13 CCR 1968.2
- bosch-mobility.com: high pressure pump cp4
- denso-am.eu: common rail suction control valve scv
- denso-am.eu: fourth generation common rail diesel diagnosis suc
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.