OnStar Schematics

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. 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 Controls

Courtesy of GENERAL MOTORS CORP.