P0004 moderate

Fuel Volume Regulator Control Circuit High

The P0004 code means the vehicle's onboard diagnostic system has detected: Fuel Volume Regulator Control Circuit High. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $150 - $600 (parts and labor)

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Common Symptoms

Check Engine Light on
Excessive fuel rail pressure
Engine runs rough
Black smoke from exhaust

Probable Causes (Ranked by Likelihood)

Short to power in fuel volume regulator wiring Very High
Failed fuel volume regulator stuck in high flow position High
Corroded ground connection for regulator circuit Moderate
ECM internal fault on regulator driver Low

Step-by-Step Diagnostic Procedure

Disconnect the fuel volume regulator and check if the code clears; if it does, the regulator is likely shorted internally
Measure voltage at the regulator connector with it unplugged; voltage above spec indicates a short to power in the harness
Verify the regulator ground path with an ohmmeter; resistance should be near zero
Monitor fuel rail pressure with regulator disconnected vs connected to determine if regulator is stuck open

Frequently Asked Questions

What does circuit high mean for P0004?

Circuit high means the ECM is detecting higher voltage than expected in the fuel volume regulator circuit. This typically indicates a short to battery voltage in the wiring or a faulty regulator solenoid with excessive resistance.

Can excessive fuel rail pressure damage my engine?

Yes. Excessively high fuel rail pressure can cause injectors to deliver too much fuel, leading to engine damage over time. It can also stress fuel system seals and gaskets, potentially causing leaks.

Is P0004 common after fuel system service?

It can occur if a connector was not properly reconnected or if wiring was pinched during reassembly. Always double-check all electrical connections after any fuel system service near the high-pressure pump.