CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 1977

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Overview

ISX – Aftertreatment Fuel Injector SMALL | MEDIUM | LARGE

ISM – Aftertreatment Fuel Injector SMALL | MEDIUM | LARGE

Circuit Description

The aftertreatment fuel injector is used to inject fuel into the exhaust system. Diesel fuel is sprayed into the exhaust system when the aftertreatment diesel particulate filter needs to be regenerated. The hydrocarbons in the diesel fuel are converted into heat in the aftertreatment diesel oxidation catalyst. The heat produced by the aftertreatment catalyst is then used to actively regenerate the aftertreatment diesel particulate filter, converting trapped soot into ash.

The aftertreatment fuel injector is electronically controlled by the engine electronic control module (ECM) through a pulse width modulated (PWM) signal. The amount of fuel injected is determined by how long the PWM signal to the injector is on.

Component Location

The aftertreatment fuel injector is installed in the exhaust system in the turbocharger outlet flange. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the engine speed is greater than 500 rpm and within the first minute of the engine starting.

Conditions for Setting the Fault Codes

The fault code will set within 30 seconds of starting the engine or prior to an active regeneration event of the diesel particulate filter.

Action Taken When the Fault Code is Active

• The ECM will illuminate the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• Current to the aftertreatment particulate trap will be disabled.
• Active aftertreatment particulate trap regeneration 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 fault code will clear within 30 seconds of starting the engine or prior to an active regeneration event of the diesel particulate filter.

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:

• An open circuit in the supply or return wire in the engine harness.
• An open circuit in the aftertreatment fuel injector solenoid.
• A short circuit to ground in the engine harness.
• A short circuit to voltage source in the engine harness.
• High resistance in the aftertreatment fuel injector solenoid.
• An extremely low resistance in the aftertreatment fuel injector solenoid (injector shorted internally but not to ground).
• A damaged ECM.

Refer to Troubleshooting Fault Code t05-1977