Cummins ISB CM850 (2003-06) Fault Code: FC0005 PID: SPN: FMI: Exhaust Gas Temperature Sensor Number 1 Circuit – Voltage Below Normal, or Shorted to Low Source. Low signal voltage or open circuit detected at the Exhaust Gas Temperature Sensor circuit.

Possible causes:

1)Signal shorted to ground
2)Signal shorted to return or ground in the sensor
3)Open circuit on the signal wire
4)Open return circuit in the harness, connector, or sensor.

This fault code will only be present in the exhaust gas treatment monitor unit and will not be present in the engine electronic control module (ECM). The exhaust gas treatment fault code and maintenance lamps will both flash five times in sequence to alert the operator that this condition exists. The engine diagnostic lamps will not illuminate.

Possible repairs:

1)Replace the exhaust gas temperature sensor.
2)Repair or replace the exhaust gas treatment monitor harness.
3)Replace the exhaust gas treatment monitor unit.