P0231

Circuit Description

The fuel pump receives power from CKT 120 through the fuel pump relay. The PCM energizes the fuel pump relay for 2 seconds at key ON to provide fuel pressure for starting. After the 2 second fuel pump prime, the PCM will not power the fuel pump relay until 4X reference pulses are received indicating that the engine is turning (crank or run). The PCM monitors voltage on the fuel pump power CKT 120 to detect fuel pump voltage supply faults. DTC P0231 is set when the PCM sees the fuel pump not energized (2 volts or less on the feedback circuit) with the engine cranking or running.

Conditions for Running the DTC

Engine speed 24 RPM or greater.

Conditions for Setting the DTC

Fuel pump feedback 2 volts or less for 1.3 seconds.

Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM will command a message to be displayed.
^ The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records.

Conditions for Clearing the Message/DTC

^ The PCM will turn the message OFF after one run and pass of the diagnostic test.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

If this DTC set without a driveability complaint look for an open between splice and PCM or poor PCM terminal contact. If a complaint did exist look for poor relay contact, relay ground, etc.

Test Description

13. When checking for circuit continuity (opens) resistance of 5 ohms or less indicates a good circuit.
When checking for shorts to ground, resistance of more than 10K ohms is usually acceptable although most readings should be infinite (OL).
23. The fuel pump fuse is powered by an ignition relay.