P0231: Fuel Pump Secondary Circuit Low

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.

Medium severity. Can I keep driving?Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

Symptoms

Engine cranks but does not start
Engine stalls while driving
Check engine light on
Blown fuel pump fuse

Most likely causes

Power wire from relay or module to pump shorted to ground (chafing at tank or underbody)
Relay contact not closing, fuse or battery feed to the relay missing
Pump motor jammed or shorted (high current)
Connector at the tank flange corroded or burnt
Pump control module faulty

What to check, in order

Start with the simplest. You can tick off each step.

Check the pump's fuse, relay, and connector
With the connector unplugged, check whether the signal wire is making contact with ground.
Replace the filter if it is due for maintenance
Compare commanded and actual pressure in live data
Measure the pressure with a suitable gauge
Check the sensor and regulator before replacing the pump

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P0231 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
2: Fuel injection
31: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0231?

Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

What causes code P0231?

The most common causes are: power wire from relay or module to pump shorted to ground (chafing at tank or underbody); relay contact not closing, fuse or battery feed to the relay missing; pump motor jammed or shorted (high current).

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.