CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 1942

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Overview

ISX – Crankcase Pressure Sensor SMALL | MEDIUM | LARGE

ISM – Crankcase Pressure Sensor SMALL | MEDIUM | LARGE

Circuit Description

The crankcase pressure sensor is used to monitor the pressure inside the crankcase. The electronic 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 in the crankcase filter assembly. The crankcase filter is located on the fuel system side of the engine. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view.

Conditions for Running the Diagnostics

The first part of this diagnostic runs at initial key-on and the second part runs when the engine is running.

Conditions for Setting the Fault Codes

The ECM detects that the crankcase pressure sensor is reading an erratic value at key-on or the crankcase pressure reading is not changing with engine operating conditions.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.

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. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

Possible causes of this fault code include:

• Disconnected crankcase breather hose between the engine outlet and crankcase filter assembly
• Resistance in the wiring harness
• A damaged in-range pressure sensor.

Refer to Troubleshooting Fault Code t05-1942