July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

OnStar Schematics

WARNING: This page is about a different car, the 2011 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Power, Ground, Serial Data, Antennas And Microphone Wiring Schematic

Courtesy of GENERAL MOTORS CORP.

Fig 2: Controls And Outputs Wiring Schematic

Courtesy of GENERAL MOTORS CORP.