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 C DTC.
The TCM shuts down and all power is removed from the solenoids.
The transmission goes to a hydraulic default mode and will operate in reverse, neutral, and first, third, or fifth range.