SPN 101 - FMI 4 (Fault Code 1844)

Crankcase Pressure Circuit - Voltage Below Normal or Shorted to Low Source

ISB, ISC, and ISL with CM2150 - Crankcase Pressure Sensor

Fault Code: 1844
PID(P), SID(S): P101
SPN: 101
FMI: 4/4
Lamp: Amber

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

EFFECT: No engine protection for high crankcase pressure.

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 rocker lever cover.

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 0.2-VDC for more than 1 second.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A default value for the crankcase pressure reading is used.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk:
Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM.

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 of this fault code include:
• Signal circuit open or shorted to ground in the engine harness or sensor
• SUPPLY wire open or shorted to ground.

Read More:
SPN 101 - FMI 3 (Fault Code 1843)
SPN 3513 - FMI 4 (Fault Code 1696)


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