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P0001 Severity
Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.
Proper diagnosis will save you time and money on unnecessary repairs.
Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.
The Fuel Volume Regulator allows the fuel system to release excessive fuel from the engine back to the fuel tank. When the engine control module (PCM) determines that the Fuel Volume Regulator is not performing properly, the PCM will set code P0001.
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Code P0001 stands for Fuel Volume Control Regulator Circuit/Open
Some diesel engines use what's called a common rail fuel injection system. With this design, all the pressure the fuel injectors need is created by an engine-driven injection pump. Fuel pressure and volume are regulated by control valves located on the pump. The fuel volume control valve (otherwise known as a fuel volume control regulator) regulates the volume of fuel produced by the injection pump.
The fuel volume control valve (FVCV) is controlled by a solenoid. The vehicle's onboard computer, the powertrain control module (PCM), controls the FVCV by turning it on and off. This allows the fuel injectors to get the volume of fuel they need. Excess fuel is routed back to the tank. A fuel pressure sensor is used to monitor FVCV performance.
Code P0001 indicates the PCM has detected a problem with the FVCV, most likely an open circuit.
Get it diagnosed by a professional
Code P0001 is typically caused by one of the following:
Sometimes P0001 can pop up intermittently. This is especially true if the code is a history code and not current. Clear the code and see if it returns. If it does, the next step is to perform a visual inspection. A trained eye can check for issues such as broken wires and loose connections. If a problem is found, the issue should be repaired and the code cleared. If nothing is discovered, check for technical service bulletins (TSBs). TSBs are recommended diagnostic and repair procedures put out by the vehicle manufacturer. Finding a related TSB can greatly reduce diagnostic time.
Typically, the next thing a technician will do is check the FVCV solenoid. The easy, but less accurate way of doing this is to measure the solenoid's internal resistance with a digital multimeter (DMM). For more precise test results, the FVCV solenoid should be tested with a digital oscilloscope. This allows the solenoid's electrical signal to be viewed directly.
If the FVCV checks out OK, its circuit should be checked next. This can be done using a DMM. The FVCV will have two wires going to it: power and ground. It should have power at all times and ground when the engine is running. If a problem is found on either side of the circuit, the factory wiring diagram can be traced to pinpoint the concern. Then, any necessary repairs can be made and the code cleared.
The PCM may interpret a problem with the FVCV if it's getting incorrect information from the fuel pressure sensor (FPS). Typically, the FPS has three wires connected to it. These are a reference signal from the PCM, a return signal to the PCM and ground.
Testing the sensor is best done with a digital oscilloscope connected to the return signal wire. This allows the technician to view the sensors signal and compare it to the factory repair information. The sensors circuit can also be checked at this time using a DMM.
In rare cases, the PCM may be at fault. The PCM should supply ground to the FVCV when the engine is running. If not, there may be a problem with the PCM or it circuit. Before condemning the PCM, its circuit should be checked for proper power and ground. It's also a good idea to check for any PCM software updated prior to replacement.
Often times code P0001 is accompanied by an engine no-start condition. If the engine runs as designed with code P0001 stored, the issue is probably intermittent.