Cummins ISM CM870 (2003-06) Fault Code: 386 PID: S232 SPN: 1079 FMI: 3/3 Sensor Supply 1 Circuit – Voltage Above Normal or Shorted to High Source. High voltage detected at sensor supply number 1 circuit.

High voltage on the (+) 5 volt supply line can be caused by a short to battery voltage in the engine harness or connectors, or a malfinctioning ECM.

Possible repair:

1)Relace the ECM.
2)Repair or replace the engine harness.
3)Replace the OEM harness.