P0004 - Fuel Volume Regulator Control Circuit High
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0004 indicates that the Engine Control Unit (ECU) has detected an unexpectedly high voltage or current in the control circuit for the Fuel Volume Regulator. This is a PWM-controlled solenoid typically located on the high-pressure fuel pump (HPFP) in Common Rail or GDI systems. 'High' usually signifies that the circuit is shorted to battery voltage (12V/24V) or that the internal resistance of the solenoid is out of specifications, preventing the ECU from accurately regulating fuel pressure by controlling the amount of fuel entering the high-pressure chamber.
Possible Causes
Short circuit to battery positive in wiring or connector
Faulty Fuel Volume Regulator (internal short in solenoid)
Damaged wiring harness rubbing against hot engine components
Failed Engine Control Unit (ECU) output driver
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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