Cummins ISB4.5 CM2150 Fault Code: 1844 PID: 101 SPN: 101 FMI: 4 Crankcase Pressure Circuit – Voltage Below Normal or Shorted to Low Source.

Circuit Description
The engine control module (ECM) provides a 5 volt supply to the crankcase pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The crankcase pressure sensor provides a signal to the ECM on the crankcase pressure sensor signal circuit. This sensor signal voltage changes based on the pressure in the crankcase filter.

Component Location
The crankcase pressure sensor is located in the crankcase filter assembly.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The ECM detects that the crankcase pressure signal voltage is less than 0.25-VDC for more than 10 seconds.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
-A default value for the crankcase pressure reading is used.

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.
-The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
-The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
-For On-Board Diagnostic (OBD) engines, the ECM will turn off the MIL after three consecutive trips where the diagnostic runs and passes.
-The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk
The crankcase 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, check for multiple fault codes.

Possible Causes
-Signal circuit open or shorted to ground in the engine harness or sensor
-Supply wire open or shorted to ground.