WARNING: This page is about a different car, the 2008 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Power, Ground, and References Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Radio to Speakers - UW6 Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: Audio Signal Communications - UQ3 Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 4: Audio Amplifier to Speakers - UQ3 Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 5: Radio to Speakers - 9C1/9C3 w/o WX7 Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 6: Radio to Speakers - 9C1/9C3 and WX7 Schematic