GM Service Manual Online
For 1990-2009 cars only
Figure 1:

Front Center of Roof in Overhead Console


Object Number: 734455  Size: SH
(1)OnStar® Button Assembly
(2)Cellular Telephone Microphone
(3)GPS Antenna
Figure 2:

Behind the Center of the I/P


Object Number: 919084  Size: LF
(1)I/P Harness
(2)Vehicle Communication Interface Module (VCIM)
(3)Vehicle Communication Interface Module (VCIM) Connectors C1 and C2