SPN 101 - FMI 3 (Fault Code 1843)

Crankcase Pressure Circuit - Voltage Above Normal or Shorted to High Source

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

Fault Code: 1843
PID(P), SID(S): P101
SPN: 101
FMI: 3/3
Lamp: Amber

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

EFFECT: No engine protection for high crankcase pressure.

Circuit Description:
The crankcase pressure sensor monitors the pressure inside the crankcase gas filter assembly. If the pressure inside the crankcase filter assembly reaches a maximum level, a fault code will be logged, indicating that maintenance is required on 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 electronic control module (ECM) detects that the crankcase pressure signal voltage is greater than 4.8-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 electronic control module (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:
• Open return circuit in the engine harness, connectors, or sensor
• Signal wire shorted to sensor supply or battery voltage.

Read More:
SPN 3513 - FMI 3 (Fault Code 1695)
SPN 3513 - FMI 4 (Fault Code 1696)


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