Cummins ISX CM870 (2003-06) Fault Code: 123 PID: P102 SPN: 102 FMI: 4/4 Intake Manifold 1 Pressure Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage or open circuit detected at the intake manifold pressure circuit

The intake manifold pressure sensor shares supply and return wires in the engine harness with other sensors. Opens and shorts in the engine harness can cause multiple fault codes to be active. Before troubleshooting Fault Code 123, check for multiple faults.

Possible causes:

1)Signal circuit open or shorted to ground in the engine harness or sensor
2)Supply line open or shorted to ground.
3) ECM Harness/Connector
4) ECM Failure

Possible repairs:

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