Conditions for Setting the DTC
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0827 sets when the transmission control module (TCM) detects a short to ground condition in the TAP up/down shift switch circuit for greater than 6 seconds when driver shift request is commanded.