Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The TAP Shift Switch Signal system allows the driver to manually shift gears by using the Upshift and Downshift positions located on the automatic transmission shift Lever. When TAP mode is selected, the shift switch input signals to the body control module (BCM). This code sets when the rolling count of the TCM does not match the same value sent from the BCM.