Powertrain, generic · Fuel and air metering, auxiliary emission controls

P0001 Fuel Volume Regulator A Control Circuit/Open

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

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.

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

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

Repair estimate

DifficultyMediumDIY possible

Parts and labour€80–2,500

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel volume regulatorhigh pressure fuel pumpfuel volume regulator wiring

References: law.cornell.edu, bosch-mobility.com, denso-am.eu, denso-am.eu.