Fault code P0231 is called “Fuel Pump (FP) Secondary Circuit Low” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0231
An internal combustion engine needs three basic components to start and run, which are air, fuel and spark or pressure. As for code P0231, it refers to fuel. The fuel system includes the tank, the low pressure pump, sometimes the high pressure fuel pump. It also includes fuel pipes and hoses, fuel pressure regulator and fuel injectors.
The fuel pump and fuel injectors are electrically controlled, so there are also fuses, relays and controller for them. Usually the controller is part of the PCM, although some cars, may have a separate fuel injector drive module.
Usually the fuel pump relay is controlled by the controller. The PCM controller grounds the fuel pump relay or primary circuit. Which then supplies power to the fuel pump using the power or secondary circuit.
On some vehicles, when the key is turned on, the pump turns on for a few seconds to fill the system.
To ensure the fuel system works properly, everything must work in concert. For example, if there is insufficient fuel pressure, the fuel injectors will not be able to deliver fuel properly. Insufficient fuel pressure can be caused by a variety of electrical problems. One of which, is a bad voltage at the fuel pump.
The PCM controller monitors the secondary fuel pump relay circuit for voltage. If the voltage falls below a certain threshold value, a DTC P0231 fault code will be set, which is defined as a low fuel pump secondary circuit voltage.
Symptoms of vehicle malfunctions
The main signal that an error P0231 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
- Other related fault codes may also be present.
- The engine may not start or may start and then stall.
- Insufficient fuel supply due to improper fuel pump operation.
- There may be no symptoms other than a stored fault code.
A fuel pump secondary circuit malfunction can cause engine starting problems, so error P0231 is considered serious. If ignored, the fuel pump may fail completely.
Factors that can cause this error code
The error code P0231 can mean that one or more of the following problems have occurred:
- The fuel pump relay is faulty and no voltage is supplied to the fuel pump.
- Damage to the wiring harness leads to an open circuit in the fuel pump power supply.
- Fuel pump may fail completely.
- Loose or damaged connectors.
- The feedback circuit is open.
- A small bump may have tripped the inertia switch which opens the fuel pump circuit.
- Fuel pump fuse blown due to short to ground.
- Faulty power control module (PCM).
How to fix or reset OBD-2 code P0231
Some suggested steps for troubleshooting and fix the error code P0231:
- Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P0231 appeared.
- Clear the error codes from the computer memory and test drive the vehicle to find out if the malfunction appears again.
- Test the fuel pump relay.
- Visually inspect the electrical wires and connections for looseness and damage.
- Check the inertia switch, turn it on if necessary.
- Replace fuse if necessary.
- Clear the error code from the computer memory again, test drive the vehicle to see if the problem is resolved.
Diagnose and repair of problems
In order to diagnose the fuel pump circuits and clear the P0231 fault code, you must have the wiring diagram for your vehicle. After that you can proceed with further actions.
If the car starts and drives, no steering complaints, there is most likely a break in the feedback circuit between the PCM and the fuel pump supply voltage circuit. Repair if necessary.
When the car won’t start or starts and shuts down because of low fuel pressure, check the fuel pump fuse. If it is blown, check the fuel pump supply circuit for a ground fault.
Remove the fuel pump relay (FP), and then check the resistance between the fuel pump connector voltage circuit and the ground. If there is a small resistance indicating a ground fault, disconnect the fuel pump and check it again.
If the fuel pump shows high or infinite resistance after disconnecting it, replace the shorted fuel pump. If the resistance is low after disconnecting the fuel pump, repair the short in the FP supply circuit.
After checking the electrical circuits, there will likely be several scenarios. Either the P0231 error will go away because the wiring problem has been corrected. Or the problem is a faulty relay or fuel pump.
On which vehicles does this problem occur most frequently
Fault code P0231 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Chevrolet (Silverado)
- Citroen
- Fiat
- Ford (C-Max, Expedition, Explorer, F-150, Focus, Fusion, Ranger, Transit, Windstar)
- GMC (Sierra)
- Hyundai
- Kia
- Mitsubishi
- Peugeot
- Renault
- Ssangyong (Kyron)
- Volkswagen
Fault code P0231 can sometimes be found with other errors. The most common are the following: P0232, P0237, P0470, P0472, P0603, P0693, P069E, P1000, P1280, P1690, B1362.
