CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 2636

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Overview

ISX – VGT Actuator Circuit SMALL | MEDIUM | LARGE

ISM – VGT Actuator Circuit SMALL | MEDIUM | LARGE

Circuit Description

The variable geometry turbocharger (VGT) is electronically activated by the VGT actuator. The VGT actuator is a smart device that receives information via the J1939 data link from the primary engine electronic control module (ECM). The VGT actuator performs its own diagnostics and reports failures back to the primary engine ECM using the J1939 data link.

Component Location

The VGT actuator is located on the turbocharger bearing housing. Refer to Procedure 100-002 in Section E.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes

The primary engine ECM does not receive a valid J1939 message from the VGT actuator for more than 1 second.

Action Taken When the Fault Code is Active

• The ECM illuminates the red STOP ENGINE light immediately when the diagnostic runs and fails.
• The VGT will move to the default open position.

Conditions for Clearing the Fault Code

The ECM will turn off the red STOP ENGINE light and enable VGT operation immediately after a valid J1939 message is received from the VGT actuator.

Shop Talk

This fault code logs when the primary engine ECM did not receive valid J1939 information from the VGT actuator.

Troubleshoot high inactive counts of Fault Code 2636 as an active fault code.

Possible causes of this fault code include:

• The VGT actuator is not receiving power from the ECM. This could be caused by an open circuit in the power supply wire or low voltage supplied by the primary engine ECM
• Rapid cycling of the keyswitch
• An open return circuit on the VGT actuator circuit
• An open or short circuit on the J1939 data link circuit between the ECM and VGT actuator
• Intermittent communications between the VGT actuator and the primary engine ECM on the J1939 data link
• Connector pins are not installed in the appropriate locations specified by the wiring schematic
• A damaged termination resistor in the engine data link harness
• A damaged engine ECM.

The aftertreatment system must be inspected after making the appropriate repair outlined in this fault code troubleshooting tree. Progressive damage to the aftertreatment system may have occurred. Perform the Snap Acceleration Test to check for a malfunctioning diesel particulate filter. Refer to Procedure 014-013 in Section 14.

Refer to Troubleshooting Fault Code t05-2636