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P0004 OBD Fault Code (Causes & Fixes)

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Last Updated on: 7th September 2023, 12:44 am

A P0004 diagnostic trouble code relates to the electrical circuit that connects to your fuel pressure regulator.

Fault CodeFault LocationProbable Cause
P0004Fuel volume regulator control -circuit highWiring open circuit/short to positive, regulator control solenoid

P0004 is a generic OBD code that indicates that the engine control module (ECM) is unable to receive signals from the fuel shut-off on the fuel injection rail attached to the engine.

When you switch off the engine, the ECM utilises the fuel shut-off valve to prevent fuel from entering the engine.

It may potentially be linked to the following codes; P0001, P0002, P0003, P0006, or P0007.

What P0004 Means

This code is related to the electrical circuit that links to your fuel system, and it’s most frequent on diesel engines.

P0004 is a generic OBD code that indicates that the engine control module (ECM) is unable to receive signals from the fuel shut-off on your fuel injection rail attached to your engine.

When you switch off the engine, the ECM utilises the fuel shut-off valve to prevent fuel from entering the engine.

It stops your engine from continuing to run after you switch off the key (a process known as “dieseling”). This code will result in a check engine light (MIL) being illuminated.

Possible Causes

The fuel shutoff valve control circuit/open code may have several causes, such as the following.

  • Possible corrosion in the sensor connector
  • A broken or damaged wire to the ECM
  • A defective fuel shutoff valve
  • Damaged ECM
  • Faulty regulator control solenoid

This failure code might also be caused by different systems and components connected to the fuel system which is why it needs to be properly diagnosed.

This code and many other DTCs might be caused by excessive heat, normal wear and tear, vibrations, shock and impacts (from potholes, for example), rubbing and friction, corrosion, and so on.

Signs & Symptoms

The P0004 code will typically cause the check engine light (MIL) to illuminate on the instrument panel/dash, and it will most likely result in the following symptoms.

  • After you switch off the key, your engine will continue to run
  • Your engine would not start due to a lack of fuel pressure
  • While driving, there’s a chance the engine will stall


Your car may experience the following problems as a result of this error code.

  1. Increase your fuel use
  2. The engine may not start
  3. The engine may not turn off after key switched to off
  4. While driving, cause your car to stall at any moment
  5. Prevent your car from passing emission tests


P0004 is diagnosed using a voltage metre and a sophisticated scan tool capable of factory sensor readings (not simply one from an auto parts shop).

The data from the advanced scan tool should be reviewed to establish when the issue first started and whether it is still happening.

They may clear the code and test drive the car while keeping an eye on the scan tool data to see whether the problem persists or returns.

Cutting open the protective covering, checking the wire harness, and replacing the covering may be required.

Further diagnostics may be necessary depending on the test circumstances, which may include clearing the code and completing a road test while monitoring the data.

Multiple instruments may be required for diagnosis, such as the following.

  • To read the ECM data values, you’ll need a sophisticated scan tool
  • A digital voltage metre

How to Fix the P0004 Error Code

The following is the most typical approach for fixing the P0004 code.

  1. Connect a professional scanner to check for the code.
  2. For testing and values based on the code, do research from professional sources.
  3. Look for any additional error codes that might be connected to the problem.
  4. Clear the trouble codes to observe which ones reappear again.
  5. Analyze data from the ECM scan tool.
  6. With additional equipment connected, road test the car while reviewing scan tool data from the ECM.
  7. Check to see whether the P0004 code appears or if the symptoms are present.
  8. Examine all of the above-mentioned elements (wiring, voltages, etc).
  9. If the problem seems to be recurring, use the specific tools described above to further diagnose the issue. The sensor’s signals and wiring must be analysed to pinpoint the source of the issue. If the indications are normal, further examination of the wiring, computer, or fuel system is necessary.
  10. Replace any defective parts, such as the fuel cutoff valve or wiring.

Replacing the fuel pressure shutdown valve alone does not ensure a successful repair, and it may be highly costly and time consuming.

It might be caused by one or more of the components mentioned above in the electrical system and wiring.

Before replacing the fuel cutoff valve, a visual check and testing with the specific equipment indicated further above can confirm your problem.

Any electrical code might appear often or seldom. Some error codes may take longer to diagnose than others.

The remedy for this code might be easy to change or take a long time to diagnose and correct.

Depending on your car, determining the underlying cause and repairing the defective component might take several hours.

The P0004 code affects a number of systems and requires a thorough investigation.

A technician can establish whether the fuel pressure regulator, wiring, or another component is at fault after utilising a scan tool and watching the voltage data from a voltmeter.

Review the data while checking the voltage metre to confirm all of the results are sufficient, meet requirements, and undertake a visual examination with the scan tool attached.

If the voltage or signal isn’t what you’re looking for, you’ll need to do some further investigating.

The sensor might be the problem, or you could have a broken ECM.

Wire difficulties could be caused by burning/rubbing on another engine component, pests could have chewed wiring in the car, connections could be shorted or damaged, or you could have a bad ECM.

Higher-mileage vehicles may just need a fuel cutoff valve replacement. Replacing components based on a code, on the other hand, is not advised and has resulted in issues or failure to address the issue.

  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer. He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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