WARNING: This page is about a different car, the 2007 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: BCM Power, Ground, and Serial Data Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: BCM Inputs and Outputs (1 Of 4) Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: BCM Inputs and Outputs (2 Of 4) Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 4: BCM Inputs and Outputs (3 Of 4) Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 5: BCM Inputs and Outputs (4 Of 4) Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 6: Rear Body Control Module References (Export w/ UTA/UTB/UTC) Schematic