I found this place and from the looks of it , it depends on what aftermarket radio you would be using .
http://www.pie.net/pie_store/shopdisplayproducts.asp?id=137&cat=Steering+Wheel+Control+Interfaces
http://www.pie.net/pie_store/shopdisplayproducts.asp?id=137&cat=Steering+Wheel+Control+Interfaces