Cummins ISB CM850 (2003-06) Fault Code: 2555 PID: SID 70 SPN: 729 FMI: 3 Intake Air Heater #1 Circuit – Voltage Above Normal or Shorted to High Source. High voltage detected at the intake air heater signal circuit.

Cummins ISB CM850 (2003-06) Fault Code: 2555 PID: SID 70 SPN: 729 FMI: 3 Intake Air Heater #1 Circuit – Voltage Above Normal or Shorted to High Source. High voltage detected at the intake air heater signal circuit.

Possible causes:

1)Intake air heater relay signal wire not connected to the relay
2)Intake air heater relay return wire not connected to the relay
3)Open circuit in the intake air heater relay signal wire
4)Open circuit in the intake air heater relay return wire
5)Intake air heater signal wire shorted to a voltage source.

Possible repairs:

1)Flush the dirt, debris, or moisture from the connector pins.
2)Install the appropriate connector seal if it is damaged or missing.
2)Replace the intake air heater relay.
4)Replace the OEM harness
5)The removal and installation of the connector may correct the fault.
6)Replace the ECM.