CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 3734

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Overview

ISX – Crankcase Breather Filter Heater Circuit SMALL | MEDIUM | LARGE

ISM – Crankcase Breather Filter Heater Circuit SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) controls the crankcase breather filter heater by sending a signal. The ECM will only command the crankcase breather filter heater ON under certain operating conditions.

Component Location

The crankcase breather filter heater is located on the front cover of the crankcase breather filter housing. Refer to Procedure 100-002 in Section E.

Conditions for Running the Diagnostics

The feature must be enabled. It runs any time the ECM is keyed ON.

Conditions for Setting the Fault Codes

If the output driver is on, the ECM checks if the voltage output to the crankcase filter heater is high. If not, the driver is shorted to ground, the fault is reported, and the output will be disabled until the next key cycle.

If the output driver is off, the ECM checks if the voltage output to the crankcase filter heater is high. If not, the driver has an open circuit and the fault is reported. The output driver will still function normally.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE LIGHT.

Conditions for Clearing the Fault Code

For a short to ground, the keyswitch must be cycled.

Shop Talk

Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable corrections to the calibration stored in the ECM. If necessary, calibrate the ECM. Refer to Procedure 019-032 in Section 19.

The ECM monitors the voltage level on this circuit.

Possible causes for this fault code include:

• A short circuit to a voltage source
• A damaged or missing heater element
• Wiring harness issue
• Pins incorrectly installed in harness
• Damaged connectors.

Refer to Troubleshooting Fault Code t05-3734