2004 gm bose 6 disc no xm

Newby here looking for some help. I have a 2004 gm Bose 6 disc factory head unit without xm. I want to wire an aux jack into the preamp signal that would normally come from the xm module. The problem I have is when I try to select xm from my head unit the head unit only displays options for cd. Does the head unit need to be programmed in order to see the xm option or does the xm module send some kind of machine signal to the head unit that xm is an available option ? In other words I just need to know how to get the head unit to display xm. I'm not planning on using the xm option for anything but wiring in an aux input. Thanks to anyone that can assist !