CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 1993

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Overview

ISX and ISM – Aftertreatment Differential Pressure Sensor SMALL | MEDIUM | LARGE

Circuit Description

The engine aftertreatment system monitors for the presence of the aftertreatment diesel particulate filter. This diagnostic checks to make sure the aftertreatment diesel particulate filter is present and functioning correctly.

Component Location

The aftertreatment diesel particulate filter is located in the exhaust system and is installed by the original equipment manufacturer (OEM). Refer to the OEM service manual.

Conditions for Running the Diagnostics

This diagnostic runs when the engine is running and exhaust flow is above a minimum level.

Conditions for Setting the Fault Codes

This diagnostic monitors the aftertreatment diesel particulate filter differential pressure sensor. When the differential pressure is below a minimum value and the exhaust flow rate is above a minimum flow rate, this fault code is set.

Action Taken When the Fault Code is Active

• The ECM will illuminate the amber CHECK ENGINE light immediately after the diagnostic runs and fails.
• Active regeneration of the aftertreatment diesel particulate filter will be disabled.
• The exhaust gas recirculation (EGR) valve operation will be disabled.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

The conditions for clearing this fault code require that the exhaust flow be above a minimum value before the fault code will become inactive. The exhaust volumetric flowrate as monitored in INSITE™ electronic service tool must be above 14.1 ft3/sec for a consecutive 30 seconds for the fault code to become inactive. It will be necessary to elevate the exhaust flow above this minimum flowrate value by taking the engine to maximum governed engine speed.

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, calibrate the ECM. Refer to Procedure 019-032 in Section 19.

Possible causes of this fault code include:

• The aftertreatment diesel particulate filter has been removed from the vehicle.
• The aftertreatment diesel particulate filter is cracked or broken.
• The aftertreatment diesel particulate filter differential pressure sensor tubes are installed incorrectly, broken, loose, or have been tampered with.
• The aftertreatment diesel particulate filter differential pressure sensor tubes are installed backwards.

Refer to Troubleshooting Fault Code t05-1993