WARNING: This page is about a different car, the 2003 Chevrolet Monte Carlo and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Antenna, Grounds, Power & References To DLC, Lighting & OnStar Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Audio Amplifier Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 3: Digital Radio Receiver Schematic (U2K) (Early Production)
Courtesy of GENERAL MOTORS CORP.
Fig 4: Digital Radio Receiver Schematic (U2K) (Late Production)