P0231

CIRCUIT DESCRIPTION
The status of the fuel pump is monitored by the powertrain control module (PCM). This signal is also used to store a diagnostic trouble code (DTC) if the fuel pump relay is defective or fuel pump voltage is lost while the engine is running. There should be about 12 volts on circuit 120 during glow plug cycle.

CONDITIONS FOR RUNNING THE DTC
^ The PCM performs this DTC diagnostic continuously.
^ The fuel lift pump is commanded ON.

CONDITIONS FOR SETTING THE DTC
^ The difference between ignition voltage and fuel pump voltage is more than 4 volts.
^ All diagnostic conditions are met for 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module stores the DTC information into memory when the diagnostic runs and fails.
^ The malfunction indicator lamp (MIL) will not illuminate.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
^ The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC Last Test Failed clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ Clear the DTC with a scan tool.

DIAGNOSTIC AIDS
This DTC will not check the fuel pump operation.

TEST DESCRIPTION

Steps 1-11:

Steps 12-20:

The number below refers to the step number on the diagnostic table.
3. This step checks the fuel lift pump circuit.