WARNING: This page is about a different car, the 2005 GMC Canyon and 2005 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Power, Ground, Serial Data & Controlled/Monitored Subsystem Reference Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Subsystem References To Theft, Horn, Seat Belt, Outside Mirror, RAP, Brake Warning, ABS & Wiper/Washer Systems Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: Subsystem References To Interior Light & Interior Lights Dimming Systems Schematic