P0231

Diagnostic Chart:

Wiring Diagram:

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 defective 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 SETTING THE DTC

^ The fuel lift pump is commanded ON.

^ 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 tails.

^ 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 will clear after forty consecutive warm-up cycles during which the diagnostic does not fail (the coolant temperature has risen 5°C (40°F) from start up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) of that same ignition cycle).

^ Use of a Scan Tool will clear the DTC codes.

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.

13. 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.