XM and rear DVD audio problem

[Cursed Yukon]

This new to me yukon doesn't disappoint me with surprises. Trying out the rear DVD player tonight I found out the XM some how still works (even though factory stereo is gone) it plays both XM preview with DVD audio very faint behind it in the wireless headphones. How can I make the XM stop playing through. (Upon further inspection I found the factory harnesses has been butchered and no longer in place and the rear radio and HVAC controls no longer work. It has a pioneer mxtrax double din that I would love toss in the garbage)