SPN 641 - FMI 9 (Fault Code 2636)

SPN 641 FMI 9
VGT Actuator Driver Circuit - Abnormal Update Rate

ISB, ISC, and ISL - VGT Actuator Circuit

Fault Code: 2636
PID(P), SID(S): S027
SPN: 641
FMI: 9/9
Lamp: Red

REASON: VGT Actuator Driver Circuit - Abnormal Update Rate. No communications on the J1939
data link between the engine ECM and the smart VGT controller.

EFFECT: The VGT will move to the default open position.

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 malfunctions back to the primary engine ECM, using the J1939 data link.

Component Location:
The VGT actuator is located on the turbocharger bearing housing.

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:
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.

This fault code is logged when the primary engine ECM does 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.
• 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.
• Rapid cycling of the keyswitch.
• Connector pins are not installed in the appropriate locations specified by the wiring diagram.
• A damaged termination resistor in the engine data link harness.
• A damaged engine ECM.

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