Action Taken When the DTC Sets

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0634 is a Type A DTC.
The TCM shifts to a default gear, shuts down, and turns OFF.
The TCM disables TAP shift operation.
The TCM enables torque management.