I purchased a XM receiver on eBay. The car did not have XM before but the A4's was pre-wired. The radio is not recognizing the unit (which I was told was tested) and from doing some research on the various forums there are some comments that the Can Bus has to be changed/modified if it is a first time install.

Does anyone have any idea as to how I would do this? There was at least one forum post that gave thorough install instructions but the link within that post to info on Can Bus mods was broken.

I would appreciate any help.

Thank you.