P0004: volume regulator a control circuit high. Diagnose the circuit before replacing parts.
Meaning, symptoms, causes and checks
The volume regulator A control circuit reports a high electrical condition. Depending on the system, voltage or current is monitored; this does not automatically mean high fuel pressure.
Affected system: Powertrain
Symptoms
- Hard starting or no start if fuel delivery is affected.
- Engine warning lamp; reduced power or stalling.
Possible causes
- Short to supply or abnormal coil electrical load, according to the monitor used.
- Internal actuator or control-driver electrical fault after wiring is excluded.
What to check
- Identify fuel volume regulator A by VIN and check wiring and subcodes before measuring.
- Save failure conditions and related codes; establish whether volume regulator a is commanded when the fault returns.
- Inspect connector, heat/vibration-exposed wiring and shared supplies before replacing components.
- Test for shorts to supply and coil current by the OEM method; high does not always mean overvoltage.
- Compare command and electrical response with engine specifications; verify the repair under the original conditions.
Also written as: P0004-00, P000400, PO004 (some scan tools add the fault-type byte, e.g. -00).