P0231: Fuel pump secondary circuit low

What P0231 means

The secondary circuit carries the current from the relay to the pump. The ECU monitors that wire and here it sees too low a voltage when the pump should be running. If the pump does not get enough current it gives low pressure or stops, and the engine runs out of fuel.

Most common causes

• Blown fuel pump fuse
• Fuel pump relay with burnt contacts
• Corroded or loose pump connector near the tank
• Broken wire or poor ground between the relay and the pump
• Worn or sticking fuel pump
• Inertia fuel cut-off switch triggered, on cars that have one

Symptoms

• Engine warning light on
• Car will not start
• Engine cuts out or loses power when accelerating
• Long cranking

Can you drive with P0231?

With care If it starts and runs well you can drive carefully to a garage, but it may cut out suddenly. Avoid long trips and fast roads until it is checked.

How to check it

With the ignition on, listen for the pump running for a few seconds near the tank. If the reader shows fuel pressure, watch it live: if it drops when accelerating or is below normal at idle, suspect the pump or its power supply.

How to read and clear P0231 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0231 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

• P0221 Throttle or pedal position sensor B range or performance problem
• P0222 Throttle or pedal position sensor B circuit low
• P0223 Throttle or pedal position sensor B circuit high
• P0230 Fuel pump primary circuit malfunction
• P0232 Fuel pump secondary circuit: high signal
• P0234 Turbocharger or supercharger A overboost
• P0235 Turbo boost pressure sensor A: circuit fault
• P0236 Turbo boost pressure sensor A: range or performance problem
• P0200 Injector circuit malfunction
• P0201 Injector circuit malfunction, cylinder 1
• P0202 Injector circuit malfunction, cylinder 2
• P0203 Injector circuit malfunction, cylinder 3

P0231 is a generic code, so it means the same on any make, for example on BMW, Citroën, Ford, Mercedes-Benz, Renault, Volvo. See what Final OBD does on your car in makes and models.