WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Radio, Amp, Radio/HVAC Control (U2R/U2S) Power, Ground and Communication (UQA) Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Radio, Amp Power, Ground and Communication (UQS) Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: Speakers (UQA) Schematic (1 of 2)
Courtesy of GENERAL MOTORS CORP.
Fig 4: Speakers (UQA) Schematic (2 of 2)
Courtesy of GENERAL MOTORS CORP.
Fig 5: Noise Compensation Microphone, Navigation Audio Inputs, and Speakers (UQS) Schematic (1 of 2)