WARNING: This page is about a different car, the 2011 Chevrolet Cruze. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Low Speed GMLAN Wiring Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: High Speed GMLAN Wiring Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: Chassis Expansion Bus Wiring Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 4: Enable Serial Data Wiring Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 5: Local Interconnect Network (LIN) Serial Data Wiring Schematic