WARNING: This page is about a different car, the 2003 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Navigation System Schematics - Radio And RCA Jack Signals
Courtesy of GENERAL MOTORS CORP.
Fig 2: Navigation System Schematics - Traffic Information Receiver
Courtesy of GENERAL MOTORS CORP.
Fig 3: Navigation System Schematics - GPS Antenna, Radio