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

P0004 Fuel Volume Regulator A Control Circuit High

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. 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.

Likely causes

Short to battery voltage in the harness
Open coil or wire, reported as high with ground-side switching
Connector fault at the regulator
Output driver in the engine control module faulty

Symptoms

  • Check engine light on
  • Loss of power or limp mode
  • Rough running or diesel knock possible
  • Excess 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

Related codes

P0001P0002P0003P2373P0088P000F

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