P0004
Fuel Volume Regulator Control Circuit HighP0004 is a generic OBD-II powertrain diagnostic trouble code: Fuel Volume Regulator Control Circuit High. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0004 means
P0004 — Fuel Volume Regulator Control Circuit High — is set when the PCM/ECM detects a voltage on the fuel volume regulator (FVR) control wire that is higher than the commanded value, typically indicating a short to 12 V supply or an open in the low-side return path. The FVR is a solenoid-operated valve that the ECM pulses via PWM (pulse-width modulation) to control the volume of fuel delivered into the high-pressure pump on common-rail diesel systems; some petrol direct-injection systems use an equivalent fuel pressure regulator.
Because the FVR controls rail pressure directly, a stuck-high circuit prevents the ECM from reducing pressure. On normally-open valve designs this can cause chronic over-fuelling and black smoke; on normally-closed designs the rail may be starved of fuel at high loads, causing power loss or a no-start condition. Either scenario represents a critical fault on common-rail diesel engines where rail pressure is tightly managed.
The fault may be intermittent — caused by chafed wiring that contacts chassis ground or battery positive only under heat or vibration — so wiring inspection should precede component replacement. The ECM driver circuit for the FVR can also fail internally, producing a persistently high signal even with the solenoid disconnected.
Common causes
Most-frequently reported root causes when P0004 is logged.
-
1
Short to 12 V battery voltage in the FVR control wire or harness connector.
-
2
Open circuit on the low-side (ground) return path of the FVR solenoid, causing the ECM to read a high-side voltage.
-
3
Failed fuel volume regulator solenoid with an internal open coil, removing the load that normally pulls the signal line low.
-
4
Corroded or backed-out FVR connector pins creating a high-resistance or open low-side path.
-
5
Failed ECM/PCM output driver for the FVR channel producing a permanently high signal.
-
6
Damaged wiring insulation allowing contact with 12 V rail (common near turbo or exhaust heat sources).
-
7
Incorrect aftermarket fuel pressure regulator installed with incompatible resistance or valve type.
Symptoms drivers notice
How to diagnose P0004
A typical diagnostic flow when this code is present.
-
1
Connect a scan tool and record live fuel rail pressure; compare to the ECM-commanded target to confirm actual vs. desired mismatch.
-
2
Inspect the FVR wiring harness and connector for visible chafing, melting, corrosion, or pushed-back pins.
-
3
With the ignition ON and the FVR connector unplugged, measure voltage on the signal wire — any significant positive voltage (>1 V) indicates a short to supply.
-
4
Measure FVR solenoid resistance across its terminals; compare to manufacturer specification (typically 1–5 Ω for a healthy coil; OL indicates open coil).
-
5
Check the low-side return wire continuity from the FVR connector back to the ECM pin; an open reading confirms a broken ground path.
-
6
Reconnect the FVR, clear the code, and perform a live-data road test to verify fuel rail pressure control returns to normal.
-
7
If the fault persists with a known-good FVR and clean harness, suspect an internal ECM driver fault and consult factory wiring diagrams before replacing the ECM.
Related powertrain codes
Frequently asked questions
Can I drive with a P0004 code?
Driving is not recommended. On common-rail diesel engines the fuel rail pressure may be uncontrolled, risking over-fuelling, injector damage, or a no-start condition; pull over safely and diagnose before continuing.
Is P0004 the same as P0001 or P0003?
They share the same subsystem: P0001 is circuit range/performance, P0002 is circuit low, P0003 is circuit low (alternate), and P0004 is circuit high — each pointing to a different electrical fault direction on the same FVR solenoid.
Will replacing the fuel volume regulator always fix P0004?
Not necessarily. The 'high' designation means the circuit voltage is too high, which often points to a wiring short-to-voltage or open ground rather than a failed solenoid. Always test the circuit electrically before replacing the regulator.
Does P0004 affect petrol (gasoline) engines?
Yes, though it is far more common on common-rail diesel engines. Some petrol direct-injection systems use a high-pressure fuel volume control valve driven in the same way, and can set this code if the control circuit faults.
Disabling P0004 in software
RaceTune can permanently disable P0004 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0004 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file