WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: DLC Power Ground and Low Speed GMLAN Schematics
Courtesy of GENERAL MOTORS CORP.
Fig 2: DLC High Speed Serial Data Schematics
Courtesy of GENERAL MOTORS CORP.
Fig 3: DLC High Speed Serial Data Wake Up Schematics
Courtesy of GENERAL MOTORS CORP.
Fig 4: Local Interconnect Network (LIN) Schematics