P0001: Fuel Volume Regulator Control Circuit/Open

What does P0001 mean?

The fuel-volume regulator control circuit is open, so the computer cannot reliably control fuel entering the high-pressure pump. This system is common on common-rail diesels and gasoline direct-injection engines; the exact regulator arrangement varies by engine.

Generic OBD-II definition: Fuel Volume Regulator Control Circuit/Open. Confirm applicability in your vehicle service information.

Common causes

• Disconnected regulator plug or broken wire
• Internally open regulator solenoid
• High resistance from corroded terminals

Symptoms

• Hard starting or no start
• Reduced power or limp mode
• Check engine light

Diagnostic focus

This is an open-circuit diagnosis, not evidence that the tank is empty. Inspect recent pump-area work and unplugged connectors before considering a replacement high-pressure pump.

Can I keep driving with P0001?

Severity: High Avoid driving if the engine stalls, leaks fuel, or runs roughly. High-pressure fuel testing belongs with a qualified technician; never loosen a fuel rail or injector pipe to check pressure.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Inspect the regulator harness and plug
• With the system safely powered down, check circuit continuity and the regulator winding to the vehicle specification.
• Replace only the valve or wiring proven faulty

Sources & review

• OBD-Codes.com: P0001
• TroubleCodes.net: generic code definitions

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.