OnStar Schematics

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Module Power, Ground, and Serial Data

Courtesy of GENERAL MOTORS CORP.

Fig 2: Communication Signals and Control

Courtesy of GENERAL MOTORS CORP.