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.

Note: Use a multimeter to manually check components.

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

Open Circuit - C573/9 (UP) to C635/18 (UP).
OPEN_CIRCUIT
^ 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.

Note: Use a multimeter to manually check components.