July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!
Data Communication Schematics
WARNING: This page is about a different car, the 2010 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Power, Ground, and High Speed Serial Data (without HP7)
Courtesy of GENERAL MOTORS CORP.
Fig 2: Power, Ground, and High Speed Serial Data (HP7)