P1231

DTC P1231
Fuel pump relay fault Drive cycle A:Signal out of range - below minimum.

Possible causes by suggested order of priority:
- Fuel pump relay faulty.
- Connector(s) C573,ECM C635 (B).
- Open circuit - C573/9 (UP) to C635/18 (UP).
- Fuel pump relay driver (in ECM) fault.

Fuel pump relay faulty.
CHECK THE FOLLOWING:
- If available check fuel pump relay by substituting a known good unit.
- Use a multimeter to check the resistance of the relay coil. This should be between 40 and 150 Ohms.
POSSIBLE FAULTS
- Faulty relay.
- Use a multimeter to manually check components.

Connector(s) C573,ECM C635 (B).
- Check for connector not correctly latched, backed out pins, damaged pins, corroded pins

Open circuit - C573/9 (UP) to C635/18 (UP).
- Check resistance > 1M Ohm

Fuel pump relay driver (in ECM) fault.
CHECK THE FOLLOWING:
- Fuel pump relay never energized or fuel pump relay always energized (pump runs continuously).
- Short circuit, Open circuit and connector problems have been eliminated.
POSSIBLE FAULTS
- Faulty ECM - Relay drive circuit not working.
- Use multimeter to manually check components.