Conditions for Setting the DTC: P0816
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.
The BCM detects a stuck ON downshift switch for 3 seconds in PARK, REVERSE, NEUTRAL, or D6 and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, or D6.