Cummins ISM CM870 (2003-06) Fault Code: 2312 PID: S20 SPN: 635 FMI: 11/31 Timing Actuator Number 1 Circuit Error. Error detected on the front timing actuator circuit.

Possible causes:

1)Open circuit in the engine harness, connectors, or actuator
2)Short circuit to ground in the engine harness or actuator
3)Short circuit to voltage source in the engine harness
4)Low or high resistance in the actuator.

Possible repairs:

1)Replace the timing actuator.
2)Repair or replace the engine harness.
3)Replace the ECM.