What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles. Although generic, specific repair steps may vary by make/model.
The fuel pump is powered by the fuel pump relay. When the PCM (Powertrain Control Module) activates the fuel pump relay, voltage is supplied to the fuel pump and it pressurizes the fuel system. Some vehicles have a feedback circuit on the fuel pump power supply circuit. This is simply a circuit spliced into the fuel pump voltage supply. The splice is typically located near the PCM.
The PCM monitors this feedback circuit to ensure proper voltage is being sent to the fuel pump. By activating the fuel pump relay, it expects to see battery voltage on the feedback circuit. If it sees too low voltage or no voltage at all, it may set P0231.
Symptoms
Symptoms of a P0231 DTC may include:
No start
Starts and stalls
Misfire
Inadequate fuel supply
Causes
Potential causes of a P0231 code include:
Bad FP (fuel pump) relay
Chafing harness causing open in fuel pump power circuit
Loose/damaged connectors
Open in feedback circuit
Blown fuel pump fuse due to short to ground
NOTE: If no driveability complaint is present and P0231 code is stored, suspect open in feedback circuit between splice and PCM
Possible solutions
To diagnose fuel pump circuits, there is no replacement for a good wiring diagram. Try to locate one before attempting complex repair. If vehicle starts and runs and no driveability complaint is present, suspect open in feedback circuit between PCM and where it connects to fuel pump voltage supply circuit. Repair as needed.
If vehicle won’t start or starts and dies due to low fuel pressure, check fuel pump fuse. If blown, check for short to ground on fuel pump voltage supply circuit. Do this by removing FP relay, then check resistance between voltage supply circuit at fuel pump connector and ground. If you have low resistance indicating short to ground, unplug fuel pump and check again. If shows high or infinite resistance after unplugging fuel pump, replace shorted fuel pump. If resistance is still low after unplugging fuel pump, repair short in FP voltage supply circuit
If resistance check shows fuel pump power circuit is okay, check again between FP fuse and FP relay. There must be a short somewhere. Check for wiring harness chafing in certain areas. Repair as needed. If fuel pump fuse is not blown and vehicle won’t start or starts and stalls due to low fuel pressure, remove fuse and check for voltage present at fuse. Then check voltage goes from fuse to FP relay by reinstalling FP fuse and checking for battery voltage at FP relay. If FP fuse or FP relay has no voltage supply, fuel pump won’t operate. Find open in circuit and repair as needed. If FP fuse and FP relay have sufficient voltage, remove FP relay and install fused jumper wire to complete FP voltage supply circuit (Usually you do this by jumping terminals 30 and 87 in most relays – check wiring diagram to be sure). If fuel pump operates, replace faulty FP relay and recheck. If fuel pump doesn’t operate, check for voltage present (with jumper connected or by cycling ignition key with FP relay installed) at fuel pump connector at fuel tank. If voltage is present, check ground circuit is intact. If both are good, replace fuel pump. If no voltage present at fuel pump with fused jumper installed, open exists in fuel pump voltage supply circuit.