WARNING: This page is about a different car, the 2005 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Schematic - Power, Ground, and GMLAN Bus
Courtesy of GENERAL MOTORS CORP.
Fig 2: Schematic - Class 2 Serial Data Bus - LHD - 1 of 2
Courtesy of GENERAL MOTORS CORP.
Fig 3: Schematic - Class 2 Serial Data Bus - LHD - 2 of 2
Courtesy of GENERAL MOTORS CORP.
Fig 4: Schematic - Class 2 Serial Data Bus - RHD - 1 of 2
Courtesy of GENERAL MOTORS CORP.
Fig 5: Schematic - Class 2 Serial Data Bus - RHD - 2 of 2