WARNING: This page is about a different car, the 2009 GMC Yukon, 2009 Chevrolet Tahoe, and 2009 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Module Power, Ground, Serial Data, and Stop Lamp Switch
Courtesy of GENERAL MOTORS CORP.
Fig 2: Pressure Controls - 1 of 2 and Shift Controls