What P0231 means
P means powertrain (engine and transmission). The 0 marks a generic code defined by SAE, so the same number means the same thing across makes. The third character, 2, places it in the fuel and air metering, injector circuits subsystem; the last two digits identify the specific fault.
The engine computer switches the fuel pump on through a relay or a separate fuel pump control module. These codes cover the circuit that commands the pump, not the pump's hydraulic performance.
What “Circuit Low” means here
"Low" means the signal or control voltage fell below the minimum the module expects. For a controlled component such as a solenoid, relay or motor, "low" means the voltage the module sees on the control circuit is lower than it should be for the commanded state — commonly a short to ground or a missing supply, depending on how the circuit is switched.
What you may notice
Symptoms depend on the vehicle and on how the module responds to the fault. Any of these can accompany P0231:
- Engine cranks but will not start
- Stalling
- Pump running constantly or not priming at key-on
Where to start diagnosing P0231
- Listen for the pump priming for a couple of seconds at key-on.
- Check the fuel pump fuse and relay.
- Check power and ground at the pump connector, typically under the rear seat or through an access panel.
- Check fuel pressure to see whether the pump is actually delivering.
Clear the code only after recording freeze frame data: it shows the engine speed, load and temperature at the moment the fault set, which is often the best clue to reproducing it.
Live data to watch
These standard OBD2 values relate to P0231. Support varies by vehicle; a value your car does not report will simply be missing.
| Value | What to look for |
|---|---|
| Fuel rail pressure (PIDs 0x22/0x23) | Where supported, confirms pump delivery. |
| Engine RPM (PID 0x0C) | Cranking versus running. |
Related codes
Codes from the same fuel pump control circuit family. If several are stored together, the shared part — wiring, a common reference voltage, or the component itself — is the place to start.
Further reading
Frequently Asked Questions
What does P0231 mean?
P0231 is the generic SAE J2012 code for "Fuel Pump Secondary Circuit Low". In plain terms, it means the engine computer has detected a "circuit low" fault on the fuel pump control circuit.
Can I keep driving with P0231?
A fuel pump control fault can stop the engine without warning. Get it repaired before relying on the vehicle.
What should I check first for P0231?
Listen for the pump priming for a couple of seconds at key-on.
Definition source: SAE J2012 / ISO 15031-6 generic DTC definitions. This is the generic meaning that applies across makes; a manufacturer can define a code more narrowly or add its own sub-codes, so confirm against the service information for your vehicle before replacing parts. Written by the OBDAssistant engineering team — see our editorial policy.