Hi, I just bought a new 07 avalanche and bought it without Nav. because i wanted to put it in after market. I took it to a shop and they told me the new radio will not work with the original XM antenna. They installed the XM antenna that came with the new radio on the roof with the wire running down the winshield, not a pretty sight. I was wondering if any one knows if this is the case or not? I have put XM units in cars before and all it has is 2 coax cable but i have never seen the one in factory GM installs. The new head unit going in is Pioneer Z2 with XM module added.

Thanks for the help.

factory XM antenna will work fine with aftermarket XM tuner (with slightly modification at the coax connector)
too bad that stereo shop who did your install have no imagination.