What P0231 means
The fuel pump circuit has two sides: the primary circuit is the engine module's output to the fuel pump relay coil (or to a pump control module), the secondary circuit is the power circuit from relay contact or module to the pump itself.
How the engine computer detects it
P0231 means the secondary side reads low, and the meaning differs by system. Ford's relay systems read the voltage in the pump power circuit through a monitor wire: if it is missing with the pump commanded on – relay contact not closing, fuse missing, wire open or shorted to ground – the code sets after 2–5 s. GM pumps with their own power module report a short to ground as overcurrent at 18 A or more, setting the warning light in the first trip and switching the output off. The pump gets no voltage, so the engine will not start or stalls.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Engine cranks but does not start
- Engine stalls while driving
- Check engine light on
- Blown fuel pump fuse
Common causes
- Power wire from relay or module to pump shorted to ground (chafing at tank or underbody) Most likely
- Relay contact not closing, fuse or battery feed to the relay missing Most likely
- Pump motor jammed or shorted (high current) Possible
- Connector at the tank flange corroded or burnt Possible
- Pump control module faulty Less likely
How to diagnose P0231
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: fuel pump, fuel pump relay, fuel pump control module, fuel pump wiring.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0231 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Ford Expedition | 2003 | 3 | 152k |
Counts of owner complaints to the NHTSA that mention P0231 (4 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 2
- Fuel and air metering (injector circuit)
- 31
- Specific fault
Questions drivers ask
Can I drive with code P0231?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0231?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Can I fix P0231 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.