P0231

Circuit Description
The status of the lift pump is monitored by the PCM. This signal is also used in order to store a DTC if the fuel pump relay is detective or if the fuel pump voltage is lost while the engine is running. There should be about 12 volts on circuit 120 during the glow plug cycle.

Conditions for Running the DTC
The fuel lift pump is commanded ON.

Conditions for Setting the DTC
^ The difference between the ignition voltage and the fuel pump voltage is greater than 4 volts.
^ The condition was met for 2 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records.

Conditions for Clearing the MIL/DTC
^ The PCM will turn the MIL off after three consecutive trips without a fault condition.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
^ The use of a scan tool.

Diagnostic Aids
This DTC will not check the fuel pump for operation.

Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table.
2. This fuel pump can also be felt for a pulsing which will also determine if the fuel pump is working.
3. This step checks the fuel lift pump circuit.
14. This step checks if the PCM is sending a signal to turn the fuel pump ON. The Scan Tool display Lift Pump Voltage will indicate if the feed back voltage is being sent back to the PCM.