Cummins ISX CM870 (2003-06) Fault Code: 154 PID: P105 SPN: 105 FMI: 4/4 Intake Manifold 1 Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at intake manifold air temperature circuit.

The intake manifold temperature sensor shares return wires in the engine harness with other sensors. Opens and shorts in the engine harness can cause multiple fault codes to be active. Check fault codes with multiple counts first.

Possible causes:

1)Signal circuit shorted to ground in the harness or ECM.
2)Signal circuit shorted to return or ground in the sensor.

Possible repair:

1)Replace the intake manifold air temperature sensor.
2)Repair or replace the engine harness.
3)Replace the ECM.