See also:

Satellite Radio Antenna
The XM Satellite Radio antenna is located on the roof of the vehicle. Keep the antenna clear of obstructions for clear radio reception. If the vehicle has a sunroof, the performance of the XM system ...

Ending a Call
Press to end a call. ...

Customer Assistance for Text Telephone (TTY) Users (U.S. and Canada)
To assist customers who are deaf, hard of hearing, or speech impaired and who use Text Telephones (TTYs), GMC has TTY equipment available at its Customer Assistance Center. Any TTY user can communicat ...