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P0004 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


The P0004 Diagnostic Trouble Code (DTC) is a generic OBD-II code that indicates an issue with the fuel volume regulator control circuit. Vehicles with electronic fuel injection systems are often found to have them. When this code is triggered, it signifies that there is a problem with the fuel volume regulator control circuit's performance.


The fault within the fuel volume control circuit is specifically listed in the P0004 DTC. The responsibility for maintaining optimal fuel pressure on the fuel injection system rests with the volume regulator, which is also known as a fuel pressure regulator. It is designed to ensure that the engine's fuel supply is correct for combustion. A malfunctioning control circuit or failure to perform properly may result in a number of engine performance problems.


When a vehicle's diagnostic system registers a P0004 DTC code, it means that there is a problem with the fuel volume regulator control circuit. The following are some of the potential causes of this error code.

Faulty Fuel Volume Regulator

One possible cause of the P0004 code is a faulty fuel volume regulator (FVR). This component is responsible for regulating the amount of fuel that is delivered to the engine. If the FVR is not functioning properly, it can cause the engine to receive too much or too little fuel, which can result in a variety of problems.

Damaged Fuel Pump

 Another potential cause of the P0004 code is a damaged fuel pump. The fuel pump is responsible for delivering fuel from the gas tank to the engine. If the fuel pump is damaged or not functioning properly, it can cause the engine to receive too little fuel, which can lead to a variety of problems.

Clogged Fuel Filter

The P0004 trouble code may also show up in a vehicle's diagnostic system as a result of a clogged fuel filter. Before the fuel gets to the engine, contaminants must be removed by the fuel filter. A blocked fuel filter can impede the flow of fuel to the engine, which can lead to a number of issues.

Remember that these are not the only possible causes of the P0004 error code. There may be more causes for the issue, such as wiring problems or a broken fuel pressure sensor. It is advised that vehicle owners seek the advice of a skilled mechanic to identify and fix the problem.


There are a few ways that the P0004 DTC code can present itself when it registers. Engine performance is reduced when this issue code appears because it affects a fuel system component. Common signs of this error code include the following:

  • The check engine light (CEL) or malfunction indicator light (MIL) comes on.
  • When the key is turned off, the engine keeps running.
  • The inability to build fuel pressure prevents the engine from starting.
  • Driving stalling potential
  • Having the limp mode on or having no power
  • Fuel efficiency decline

The most typical symptom of this DTC code is the MIL, often known as the check engine light. It turns on when the fuel volume regulator control circuit has a problem, as determined by the engine control module (ECM). Depending on how serious the problem is, the light may be on all the time or flash.

If the engine keeps running after the key is removed, a broken gasoline volume regulator could be to blame. If the regulator malfunctions, the engine may continue to operate even after the key is turned off. The regulator regulates the amount of fuel that enters the engine.

The engine may be unable to create fuel pressure when it struggles to start. This can be caused by a gasoline volume regulator issue or a fuel pump issue. Sometimes the engine will start, but it will stall soon after.

The engine will have less power and might not be able to accelerate adequately if it goes into limp mode. This could pose a risk to your safety, especially if you're driving down a busy road.

Reduced fuel efficiency is yet another P0004 DTC code symptom. This can result in higher fuel usage if the engine is not receiving the proper amount of gasoline.


When a vehicle's onboard diagnostic system detects a P0004 DTC, it means that the fuel volume regulator control circuit is reading a higher value than the standard. The diagnostic process for this code involves several steps to identify the root cause of the issue.

The first step is to utilize a scan tool to gather any further DTCs that might be in the car's computer system. This can assist in finding any more problems that might be causing the P0004 error.

The technician will then look for any evidence of damage or wear on the fuel system's parts, such as the fuel pump, fuel injectors, and fuel pressure regulator. Additionally, they will inspect the fuel volume regulator control circuit's wiring and connectors for corrosion or damage.

If no visible issues are found, the technician may perform further tests, such as a fuel pressure test or a fuel volume test, to determine if the fuel system is functioning properly. 

They may also use a multimeter to check the resistance levels in the fuel volume regulator control circuit.

In some cases, the P0004 code may be caused by a malfunctioning powertrain control module (PCM). If all other components and wiring are functioning properly, the PCM may need to be replaced or reprogrammed. Overall, the diagnostic process for a P0004 DTC requires a thorough inspection of the fuel system components and wiring, as well as the use of specialized diagnostic tools and tests.

Common mistakes

Ignore other codes: Often mechanics and vehicle owners will concentrate only on the P0004 code, not taking into account more pertinent codes. To ensure that potential sources of error are not overlooked, it is crucial to address all codes at issue and carry out a full diagnostic procedure.

  • Neglecting the connection and connector: electrical problems may often cause P0004 code errors, for example, damaged connections or defective connectors. Unfortunately, these elements may be overlooked by certain individuals who are only concerned with the fuel volume regulator. Failure to repair the wires and connectors may result in incomplete repairs and the continuation of the code.
  • Inferring that the fuel volume regulator is constantly defective: it may be an error to assume, while P0004 refers specifically to the fuel volume regulator control circuit, that there is still a defect in itself. To find out the true cause of an issue, careful diagnostics should be carried out, as further factors such as sensor failure or wire problems can trigger a code.

How serious is this?

Depending on individual circumstances and the effect it will have on the vehicle's performance, the severity of a P0004 DTC code may differ. In general, the code indicates a problem with the fuel volume regulator control circuit, which can lead to engine performance issues, including decreased fuel efficiency and potential drivability problems. The code itself may not cause significant damage immediately, and it is necessary to resolve this issue as quickly as possible so that there are no further complications or maintenance of optimum engine performance.

What repairs can fix the codeS?

Repair manuals

Several repairs may need to be performed in order to correct the P0004 DTC code, including: 

  • Inspections and repairs of the wire harness and connectors associated with the fuel pressure regulator's control circuits: Thoroughly inspect these components. Any signs of deterioration, corrosion, missing connections, or poor insulation should be taken into account. If there are any defective components, correct them or replace them.
  • Verification and possible replacement of a fuel volume regulator: Use the right tools and procedures to verify that it is working properly. Replace the unit with a new one if it does not pass the test or is found to be faulty.
  • Evaluations and possible replacement of the fuel pressure sensors: Check to make sure that the sensor is functioning properly. If it is found to be faulty or does not contain accurate readings, consider replacing it.

Related codes

Some of the related codes that can be found alongside or in place of a P0004 code are as follows:

  • P0001: Fuel Volume Regulator Control Circuit/Open
  • P0002: Fuel Volume Regulator Control Circuit Range/Performance
  • P0003: Fuel Volume Regulator Control Circuit Low
  • P0005: Fuel Shutoff Valve "A" Control Circuit/Open
  • P0006: Fuel Shutoff Valve "A" Control Circuit Low


In conclusion, the P0004 DTC code represents a major problem that needs to be fixed right away. This error code indicates that an electrical signal is being detected by the fuel volume regulator control circuit that is outside of the normal range. If left unattended, the engine's Performance can be significantly impacted, and the car might not start or go into "limp mode."

The P0004 error code may be brought on by a malfunctioning fuel volume regulator, a damaged fuel pump, a clogged fuel filter, or a wiring problem. A mechanic will need to thoroughly inspect the fuel system and associated parts in order to identify the problem.

The mechanic can take action to fix or replace the defective parts once the problem has been located. It is important to remember that attempting to fix the problem without the necessary information or instruments may result in more harm to the car.

Overall, a motorist should seek expert help right away if they see any P0004 DTC symptoms, such as the illumination of the malfunction indication lamp (MIL) or a lack of power. Drivers may prevent more damage to their car and ensure that it keeps running safely and effectively by taking immediate action to fix the problem.

P0004 code – what does it mean & how to fix it