P0231Fuel Pump Secondary Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- 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. 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.
- What you may notice
- Engine cranks but does not start
- Engine stalls while driving
- Check engine light on
- Blown fuel pump fuse
- Likely causes
- LikelyPower wire from relay or module to pump shorted to ground (chafing at tank or underbody)
- LikelyRelay contact not closing, fuse or battery feed to the relay missing
- PossiblePump motor jammed or shorted (high current)
- PossibleConnector at the tank flange corroded or burnt
- RarePump control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.