XM Reception: Antenna
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The antenna system is a rear window defogger grid antenna. Using the defogger grid as an antenna requires circuitry to decouple the RF from the DC heater current. This is accomplished by the radio antenna module.