P0004 code meaning
Fuel Volume Regulator A Control Circuit High
Powertrain system Generic code P00xx codes Check engine light
What P0004 means
The fuel volume regulator (also called metering unit or suction control valve) is a solenoid valve on the inlet side of the high-pressure pump, used mainly on common-rail diesel engines. The engine control module pulses it to set how much fuel the pump draws in and delivers to the rail, and in this way controls rail pressure. P0004 means the voltage on the control circuit stays too high for the commanded duty cycle, typically because of a short to battery voltage, or, with a switched ground side, an open circuit. The valve can then not be energised; a normally open design delivers maximum fuel and rail pressure rises.
P0004 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0004
- Check engine light on
- Loss of power or limp mode
- Rough running or diesel knock possible
- Excess rail pressure codes possible
Common causes of P0004
- Most likelyShort to battery voltage in the harness
- PossibleOpen coil or wire, reported as high with ground-side switching
- PossibleConnector fault at the regulator
- Less likelyOutput driver in the engine control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel volume regulatorHigh pressure fuel pumpFuel volume regulator wiring
What each part of P0004 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 04 | The exact fault in that area. |
What to do next
- Note P0004 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0004
What does P0004 mean?
P0004 means "Fuel Volume Regulator A Control Circuit High". The fuel volume regulator (also called metering unit or suction control valve) is a solenoid valve on the inlet side of the high-pressure pump, used mainly on common-rail diesel engines. It is a generic code, so it means the same on every make.
Is it safe to drive with P0004?
Drive gently and only to a workshop. With P0004 the car can go into limp mode (reduced power) to protect itself.
Will P0004 fail an emissions test?
Yes, it can. P0004 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0004 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0004 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.