Modern Vehicles are compatible with a specialized fuel system that rectifies the intensity of the combustion process. Nowadays, standard rail diesel engines (CRD) are ubiquitous in the vehicle industry. They usually possess high-pressure fuel pumps that inject high-end fuel into the system. In the CRD fuel system, the power is directly inserted into the combustion chamber. A gasoline direct injection (GDI) engine works in the same way. This is a more efficient way of feeding fuel to any engine. The P0004 code is not as common as the other codes as it is mainly encountered in the CRD and GDI.
This code is a silent killer that may directly trespass into the car’s system and cause unbearable harm. So the owners who possess a car need to have proper and extensive knowledge about the fault code P0004. In this article, I have illustrated all the causes, symptoms, and possible repairing methods, so stay tuned to have emerged in the world of Troubleshooting the error codes.
What Does the P0004 Fault Code Mean?
Diagnostic trouble code P0004 denotes the “Fuel Volume Regulator Control Circuit High.” If we elaborate the meaning, it may stand as the powertrain control module or the PCM has encountered a reading in the fuel volume regulator control circuit that is high above the standard value. The fuel pressure control valve (FPCV) and the fuel volume control valve (FVCV) both work combinedly to supply the fuel to the vehicle’s main engine. A special type of sensor named the fuel pressure sensor mainly regulates both the FPCV and FVCV. As soon as you notice the engine degradation signal, you must go to the mechanic as a delay in fixing the issue may cause unbearable harm to your car’s engine. 
What are the Causes of the Error Code P0004?
The error code P0004 may appear as soon as it notices something unusual in the car’s engine. Some selective causes can make the error code happen to have appeared in the MIL, and the cause is,
- The FVR (fuel volume regulator) solenoid may face some unusual obstructions that stop the car engine.
- There could be some type of corrosion in the sensor connector that obstructs the sensor from working properly.
- The Electronic Control Module may have a broken wire issue that impedes the electricity from flowing between the engine.
- A damaged ECM may yield the error code P0004. There may be some faults in the FVCV circuit and fuel shutoff valve.
- Issues may occur in the PCM. The Fuel Volume Regulator (FVR) Control Valve harness may be set off wide open.
What are the Symptoms of the P0004 Code?
The error code P0004 may reveal some symptoms that clarify where the fault occurred in the vehicle engine. The engine may behave abruptly when it identifies the fault code P0004 in the system. Here are some of the natural symptoms of the DTC code P0004,
- The Malfunction indicator light (MIL) may start to blink, and CEL (Check Engine Light) may appear suddenly.
- Your car may not start as it turns on the limp mode, which means the internal security system of the car stops every operation in the engine to avoid unnecessary collapse of the entire system.
- The engine performance declines as it starts the process to stall the engine’s power.
- Skyrocketing fuel consumption as the whole system fails to operate and needs that extra flavor of fuel to keep the system alive for some time.
- It may destroy the exhaust system’s catalyst and cause exhaust gasses to be black or white.
How to Diagnose the P0004 Trouble Code?
The diagnosis process of the error code needs to maintain an extensive hierarchy of stages. An experienced mechanic firstly inputs the individual scanner to the individual harborage of the vehicle. The scanner must be of decent quality and should be compatible with the OBD-II system. The scanner may showcase some error codes along with the error code P0004. But they will keep the focus on the P0004 code, and gradually all other regulations should be encountered.
The next thing that the professional may give attention to is the wiring, electrical circuits, connectors, and the protocols algorithm and checks for if there are any becks, fraudulent legs, or erosion. After he has cleared all the issues that caused trouble with the engine, he goes for a test drive and checks if the problems still exist. He may remove the code with the ongoing process and see if the code comes back. They often use an advanced OBD-II scanning tool and a digital voltage meter to examine the running voltage to regulate the whole. 
How serious is the P0004 code?
There are thousands of in-built powertrain error codes dormant in the vehicle’s system. They rise when they see some technical issues in the car’s engine. Unlikely, The code P0004 is considered a severe inaccuracy of the car’s engine. They may get insane as it is sorely related to the engine of the car. It can cause serious havoc to the car’s system, like it may lower the car’s fuel economy. It may impede the vehicle from being the start and stopping. The emission of the fumes through the exit pipe could be backpedaled, and they may emit unhealthy white and black fumes. Overall the health of the engine of the vehicle could severely be hampered by the error code P0004.
What Parts to be Repaired to Fix the P0004 Code
Repairing is the sole duty of the professional; they fix the problem by fixing some of the parts one by one. The parts that are to be repaired,
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Engine Control Module
It is considered the heart of the vehicle. If this part fails, all the other systems may collapse. The MIL will be on if there is any problem in this section. Your mechanic might suggest you change or replace the whole defective part.
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Powertrain Control Module
The PCM includes the ignition and fuel injection systems and controls the emissions. PCM is a very significant part of the engine, and it receives hundreds of thousands of signals from a wide variety of sensors and switches. This section may collapse due to unavoidable issues and causes.
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Fuel Volume Regulator
The most valuable part of the fuel section is the fuel volume regulator. It mainly regulates the fuel volume injected by the fuel pump. It seems all fine in the engine control module (ECM), but still, the OBD-II flashes. Then there may be some issues with the fuel volume regulator. Replace it without any further delay.
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Fuel Volume Control Valve
The responsible valve that controls the entering of the fuel into the engine can be termed the fuel volume control valve (FVCV). As time advances, the valve gets loose or shattered, causing the unnatural flow of fuel in the engine. If the mechanic finds faults in the FVCV, he suggests replacing the whole module as the defect can cause further insecurities.
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Engine Wiring Connectors
Wiring is one of the most fundamental parts of the vehicle; it is a well-organized set of wires, cables, connectors, and terminals controlling a vehicle’s electrical system. Engine wire harnesses provide the information and signals to the battery, alternators, and other systems.
How to Repair the P0004 Trouble Code?
Thousands of issues can affect the yielding of the error code P0004. Lots of issues need to be checked to eradicate this fault code. Lets us see the repairing procedures of the fault code P0004,
- At the very first stage, the advanced OBD-II scanning tool needs to be connected to the vehicle’s system and scan or verify if the code exists. Then check for other fault codes if they exist simultaneously with the code P0004. This scanner communicates with the car’s internal computer and instructs it to delete the code.
- Then the professional will analyze the data following the ECM. Take a small test drive if the car includes all the tools attached. Then he will examine the code again if it returns an onslaught.
- Then repair all the other parts, including the electrical wiring, connectors, FVCV, voltages, and so on. Replace the fuel shutoff valve and wiring if it is needed. The professional may again attach the scanning machine after fixing all the issues. If the code does not return, then your car is ready to go.
Repairing Cost
The cost of repairing may vary according to the quality of professional, locational divergence, and functioning cost. But most auto repair shops charge between 75$ to 150$ to fix the error code P0004.
The fault code P0004 denotes a severe problem that needs to be addressed without any further delay, and it is suggested that you need to check the technical service bulletins (TSBs) to increase the functionality. It will save time and will face less effort in correcting the code. Some other codes related to the trouble code P0004 are P0001, P0002, and P0000; each is associated with the fuel volume regulator.
That is all about troubleshooting the error code P0004, and if you follow the above guidelines correctly, it won’t take a huge time to recover the code. I hope you benefited from the article, and if you have any questions related to the error codes, you can ask with a free mind.
Meet our professional car mechanic, Russell D. Steele, who has been in this field for five consecutive years and works with several automotive companies. He completed the "AUTOMOTIVE & LIGHT DUTY DIESEL TECHNOLOGY" course from NorthWest Lowa Community College, where he learned essential diagnostic and transportation management skills and became a certified mechanic.
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