Fuel Volume Regulator Control Circuit High
Code P0004 means the PCM has detected that the fuel volume regulator (FVR) control circuit voltage is higher than its expected maximum threshold. A "circuit high" condition typically points to a short to battery voltage in the wiring, a failed solenoid, or an open in the ground side of the circuit. P0004 is most common on diesel engines and GDI gasoline engines equipped with a high-pressure fuel pump.
What You Might Notice
- Check engine light on
- Hard starting or no-start
- Rough idle or engine stumble
- Reduced power or limp mode activation
- Engine hesitation under acceleration
- Poor fuel economy
Most Common Causes
- 1
Short to voltage in the FVR signal wire
A wire in the fuel volume regulator circuit has contacted a power source, forcing the circuit voltage above the PCM's maximum threshold. This is the most direct cause of a circuit-high code. Trace the harness for contact with battery positive wires or hot engine surfaces.
- 2
Open ground circuit for the FVR solenoid
If the ground side of the FVR circuit is broken or has high resistance, the solenoid cannot complete the circuit and the signal voltage reads artificially high. Check the solenoid ground wire and its chassis connection point.
- 3
Failed FVR solenoid (open coil)
An FVR solenoid with an open coil presents high resistance to the PCM, which the control circuit reads as a high-voltage condition. Test solenoid resistance — infinite resistance confirms an open coil.
- 4
Damaged or corroded connector with voltage backfeed
Corrosion or tracking inside the connector can cause voltage from an adjacent pin to backfeed into the FVR signal circuit, triggering a false high-circuit code.
How to Diagnose It
- 1
Check Short to voltage in the FVR signal wire — A wire in the fuel volume regulator circuit has contacted a power source, forcing the circuit voltage above the PCM's maximum threshold. This is the most direct cause of a circuit-high code. Trace the harness for contact with battery positive wires or hot engine surfaces.
- 2
Check Open ground circuit for the FVR solenoid — If the ground side of the FVR circuit is broken or has high resistance, the solenoid cannot complete the circuit and the signal voltage reads artificially high. Check the solenoid ground wire and its chassis connection point.
- 3
Check Failed FVR solenoid (open coil) — An FVR solenoid with an open coil presents high resistance to the PCM, which the control circuit reads as a high-voltage condition. Test solenoid resistance — infinite resistance confirms an open coil.
- 4
Check Damaged or corroded connector with voltage backfeed — Corrosion or tracking inside the connector can cause voltage from an adjacent pin to backfeed into the FVR signal circuit, triggering a false high-circuit code.
How to Fix It
- 1
Check FVR wiring for short to battery voltage
With the ignition on and the FVR disconnected, measure voltage at the signal wire. If battery voltage is present when it should not be, trace the harness for contact with a voltage source and repair the short.
- 2
Inspect and test the ground circuit
Locate the FVR solenoid ground wire and check for continuity to a known good chassis ground. High resistance or an open in this wire causes the circuit to read high. Clean or repair the ground connection.
- 3
Measure FVR solenoid resistance
Disconnect the FVR solenoid and test resistance across its terminals. Infinite resistance (open circuit) confirms a failed solenoid coil. Replace the solenoid or high-pressure fuel pump assembly.
- 4
Replace the fuel volume regulator solenoid
If electrical testing confirms the solenoid is faulty, replace it. Use an OEM or equivalent part to ensure the correct resistance specification for your vehicle.
- 5
Clear codes and verify repair
Clear all DTCs after completing repairs. Road test and rescan to confirm P0004 is resolved and fuel system pressure is within specification.
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