P0231 means Fuel Pump Secondary Circuit Low. The voltage on the fuel pump’s power circuit after the relay is lower than expected while the pump should be running. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0231 means
Modern engines measure boost and fuel rail pressure and compare them with a desired value calculated from engine speed, load and throttle. When actual pressure falls short of desired for long enough, the computer sets a code and often reduces power to protect the engine. Watching desired and actual values side by side on a scan tool shows whether the shortfall is constant or only appears under load.
P0231 symptoms
- Hard starting or no start
- Stalling
- Loss of power under load
Common causes of P0231
- Failed fuel pump relay
- Blown fuse
- Wiring or connector fault to the pump
- Failing fuel pump drawing excess current
How to diagnose P0231
- Check the fuel pump fuse and relay
- Check voltage at the pump connector while cranking
- Check fuel pressure
Can you drive with P0231?
Risky; the engine may stall.
P0231 tips
A fuel pump that draws too much current as it wears can overheat its relay and wiring; check for burned terminals at the pump connector. If the relay and fuse test good, measure voltage at the pump with the pump running; a large drop between the relay and the pump points to corroded terminals or a damaged wire.
Will P0231 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0231 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0230 | Fuel Pump Primary Circuit |
| P0232 | Fuel Pump Secondary Circuit High |
| P0087 | Fuel Rail/System Pressure Too Low |
Guides that help
When it is more than a sensor
Our superchargers page lists supercharger kits, and diesel owners can read the 6.7 Cummins turbo guide. If a failed turbo or fuel pump has damaged the engine, compare engines by code on our engines page.
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