Fuel Volume Regulator Control Circuit/Open
Code P0001 means the PCM has detected an open circuit in the fuel volume regulator (FVR) control circuit. The fuel volume regulator is a solenoid on high-pressure fuel pumps — common on diesel and gasoline direct injection (GDI) engines — that controls fuel rail pressure. An open circuit means the PCM cannot communicate with or command the solenoid, which disrupts fuel delivery and can cause hard starting, rough running, or reduced power.
What You Might Notice
- Check engine light on
- Hard starting or extended cranking
- Engine runs rough or misfires at idle
- Reduced power or hesitation under load
- Limp mode activated
- Poor fuel economy
Most Common Causes
- 1
Failed fuel volume regulator solenoid
The FVR solenoid itself has failed internally, causing an open in the circuit. This is the most common cause, especially on high-mileage diesel or GDI engines. The solenoid can be tested for resistance with a multimeter.
- 2
Open, broken, or corroded wiring or connectors
A broken wire or corroded connector in the FVR circuit prevents the PCM signal from reaching the solenoid. Inspect the harness for chafing, heat damage, or corrosion at the connector pins.
- 3
Clogged fuel filter or weak fuel pump
A severely restricted fuel filter or a failing low-pressure fuel pump can starve the high-pressure pump, causing abnormal pressure readings that trigger FVR circuit codes alongside P0001.
- 4
PCM driver failure
Rare but possible. The PCM's internal driver circuit for the FVR solenoid can fail, showing an open-circuit code even when the wiring and solenoid are intact. Rule out all other causes before replacing the PCM.
How to Diagnose It
- 1
Check Failed fuel volume regulator solenoid — The FVR solenoid itself has failed internally, causing an open in the circuit. This is the most common cause, especially on high-mileage diesel or GDI engines. The solenoid can be tested for resistance with a multimeter.
- 2
Check Open, broken, or corroded wiring or connectors — A broken wire or corroded connector in the FVR circuit prevents the PCM signal from reaching the solenoid. Inspect the harness for chafing, heat damage, or corrosion at the connector pins.
- 3
Check Clogged fuel filter or weak fuel pump — A severely restricted fuel filter or a failing low-pressure fuel pump can starve the high-pressure pump, causing abnormal pressure readings that trigger FVR circuit codes alongside P0001.
- 4
Check PCM driver failure — Rare but possible. The PCM's internal driver circuit for the FVR solenoid can fail, showing an open-circuit code even when the wiring and solenoid are intact. Rule out all other causes before replacing the PCM.
How to Fix It
- 1
Check for technical service bulletins (TSBs)
Search for TSBs for your year, make, and model related to P0001 or fuel volume regulator faults. Some manufacturers have issued software updates or known repair procedures that address this code.
- 2
Inspect FVR wiring and connector
Visually trace the wiring harness from the fuel volume regulator to the PCM. Look for broken wires, chafing on engine components, or corroded connector terminals. The FVR is a two-wire device — repair any damaged sections found.
- 3
Test and replace the fuel volume regulator solenoid
Disconnect the FVR connector and measure solenoid resistance with a multimeter. Compare to manufacturer specs. If resistance is out of range or infinite (open), replace the solenoid or the high-pressure fuel pump assembly it is part of.
- 4
Replace the fuel filter and test fuel pump pressure
A clogged filter contributes to abnormal fuel system pressure. Replace the fuel filter and perform a static fuel pressure test to confirm the low-pressure fuel pump is delivering correct pressure to the high-pressure pump.
- 5
Clear codes and verify repair with a road test
After repairs, clear all DTCs and road test under normal conditions including acceleration and highway speeds. Confirm P0001 does not return before returning the vehicle to service.
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