WARNING: This page is about a different car, the 2010 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Low Speed GMLAN Circuit Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Mid Speed GMLAN Circuit Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: High Speed GMLAN Circuit Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 4: Local Interconnect Network (LIN) Bus Circuit Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 5: Chassis Expansion BusCircuit Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 6: Communication Enable & Wake-up Circuits Schematic