PACCAR PX-9 CM2350 (2013-17) Fault Code:1844 PID:101 SPN:101 FMI:4 Crankcase Pressure Circuit – Voltage Below Normal or Shorted to Low Source

Reason:
Crankcase Pressure Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the crankcase pressure circuit.

Effect:
None on performance.

Circuit Description:
The crankcase pressure sensor is used to monitor the pressure inside the crankcase. The engine control module (ECM) supplies the crankcase pressure sensor a 5 volt reference voltage. When the crankcase pressure is low, the sensor signal voltage is low. When the crankcase pressure is high, the sensor signal voltage is near the 5 volt reference voltage. The ECM monitors the crankcase pressure signal circuit voltage to calculate the pressure of the air within the crankcase.

Component Location:
The crankcase pressure sensor is located near the crankcase ventilation filter.

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

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the crankcase pressure signal voltage was out of range low.

Action Taken When the Fault Code is Active:
1) The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2) A default value for the crankcase pressure reading is used.

Conditions for Clearing the Fault Code:
1) To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
5) 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:
1) Signal circuit open or shorted to ground in the engine harness or sensor
2) Supply wire open or shorted to ground