Fuel and air

P0231 — Fuel Pump Secondary Circuit Low Voltage

Severity: medium Drive with care, to a shop

What P0231 means

The PCM monitors voltage in the fuel pump secondary circuit, which is usually fed through the pump relay and provides feedback. If the voltage is lower than expected while the pump should be running, the PCM sets P0231. The cause can be a relay, fuse, wiring, connector, ground or the pump itself.

Symptoms

  • Check Engine light on
  • Hard starting or no start
  • Rough or unstable idle
  • Engine stalling while driving
  • Loss of power and weak acceleration

Possible causes

  1. Faulty fuel pump relay
  2. Damaged wiring or corroded connectors in the secondary circuit
  3. Blown fuel pump fuse
  4. Internal electrical failure of the fuel pump
  5. Poor ground connection
  6. Wiring shorted to ground
  7. PCM output driver fault (uncommon)

How to diagnose

  1. Scan for codes and freeze frame data and look for other fuel or power supply codes
  2. Inspect the fuel pump fuse and relay, and swap in a known good relay
  3. Listen for the pump priming when the ignition is turned on
  4. Inspect wiring and connectors at the pump, relay and PCM for chafing, corrosion and water
  5. Use a multimeter to check supply voltage at the pump connector with the ignition on
  6. Check the ground and the continuity of the feedback wire against the wiring diagram
  7. Measure pump current draw and fuel pressure
  8. If wiring and relay are good, verify the PCM control signal

Common fixes

  • Replace the fuel pump relay
  • Repair wiring or replace damaged connectors
  • Replace the fuse and fix the cause of the blown fuse
  • Clean and tighten ground connections
  • Replace the fuel pump assembly
  • Repair or replace the PCM (last resort)

Questions and answers

What does P0231 mean?

It means low voltage in the fuel pump secondary circuit. The PCM sees feedback voltage below the expected level and stores the code.

Can I drive with P0231?

Only for short distances. The pump may shut off without warning, stalling the engine, and it may not restart.

Where do I start diagnosing P0231?

Start with the fuel pump fuse and relay, then inspect connectors and grounds. If those are fine, check voltage at the pump with a multimeter.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.