Cummins ISC CM2150 (2007-09) Fault Code: 2556 PID: SID 070 SPN: 729 FMI: 4 Intake Air Heater 1 Circuit - Voltage Below Normal or Shorted to Low Source. Low voltage detected at the intake air heater signal circuit.

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

Possible causes:

1)A shorted intake air heater relay
2)Intake air heater relay supply wire shorted to ground.

Possible repairs:

1)Replace the intake air heater relay.
2)Repair or replace the OEM harness.
3)Replace the ECM.