My 2009 Sonata GLS vehicle stock radio has satellite xm radio now. I am installing an aftermarket radio that is satellite xm ready, but the company said I had to purchase a satellite xm tuner in order to use the service. Why can't I use the satellite radio connection from my stock radio? Any help would be greatly appreciated.

 

Be advised that beginning with 2008 year vehicles a CAN, controller area network ,system is part of the vehicle electronics.
Also on many of these systems the radio is one of the modules in the network and if that is so, and that module is removed the system cannot function and the people selling the radios don't tell you this.
The smart thing to do is check with your local dealership service dept and make sure you can do that change without any problems.