Cummins ISB4.5 CM2150 Fault Code: 2636 PID: SPN: 641 FMI: 9 VGT Actuator Driver Circuit – Abnormal Update Rate.

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 datalink from the primary ECM. The VGT actuator performs its own diagnostics and reports failures back to the primary ECM with 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 lamp and/or malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.

VGT actuation will be disabled.

Conditions for Clearing the Fault Code
-To validate the repair, perform a key cycle. The diagnostic will clear immediately after a valid J1939 message is received from the VGT actuator.
-The ECM will turn off the red STOP ENGINE lamp and enable VGT operation immediately after the diagnostic runs and passes.
-The ECM will turn off the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with the INSITE™ electronic service tool.

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

Possible Causes
-The VGT actuator is not receiving power from the ECM. This can 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.
– damaged termination resistor in the engine data link harness.
– damaged engine ECM.