The multi-band antenna is on the roof of the vehicle. The antenna is used for AM-FM radio, OnStar, the SiriusXM satellite radio service system, and GPS (Global Positioning System), if the vehicle has these features. Keep the antenna clear of obstructions for clear reception.
If the vehicle has a sunroof, and it is open, reception can also be affected.
Radio Reception
Audio Players#PI0574A: Missing OnStar Owner Kit Integration in Vehicle Owner Manual - (May 28, 2013)
Subject:Missing OnStar® Owner Kit Integration in Vehicle Owner ManualModels: 2012-2014 GM Passenger Cars and Light Duty Trucks This bulletin is being revised to include the 2013-2014 model year vehicles, updatethe covered models and the Recommendation/Instructions section. Please discard PI057 ...