Diagnostic trouble code

P0231 Fuel Pump Secondary Circuit Low

The PCM sees low voltage in the fuel-pump secondary circuit.

Fuel Pressure & Delivery Codes

Read This First

This code identifies the failed diagnostic test or circuit family. Confirm the basic checks before replacing parts, and keep freeze-frame data until the repair is verified.

Common Checks

  • Check fuel-pump relay, inertia switch where equipped, wiring, and pump connector.
  • Measure voltage under load instead of relying only on continuity.
  • Inspect grounds and harness damage near the tank.

Common Repairs

  • Repair relay, wiring, connector, or ground faults.
  • Replace the fuel pump only after confirming low voltage or pump failure.

Mustang Notes

Model-Year Applicability

Listed for 1996 and newer traditional gasoline Mustang pages in this first-pass catalog. Engine, calibration, and Ford-specific codes may narrow that range as more service data is added.

Sources

  1. SAE J2012DA Digital Annex of Diagnostic Trouble Code Definitions
  2. 1996 Ford Mustang Owner Guide