P0231

Diagnostic Chart:

CIRCUIT DESCRIPTION
The status of the lift pump is monitored by the Powertrain Control Module (PCM). This signal is also used to store a 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. This is a type B DTC.

CONDITIONS FOR SETTING THE DTC
- Fuel lift pump commanded ON.
- Ignition voltage minus 4 volts.
- Fuel lift pump voltage less than ignition voltage value.
- Condition met for 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
No action taken.

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

DIAGNOSTIC AIDS
A DTC P0231 will result in a poor performance problem under heavy loads or grades.

TEST DESCRIPTION
Number(s) below refer to the Step number(s) on the Diagnostic Table.

2. This fuel pump can also be felt for a pulsing, this 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 ON the fuel pump. The scan tool display Lift Pump Voltage will tell you if feed back voltage is being sent back to the PCM.