I have a 2010 Terrain with Nav system. When I turn my car off all of my XM channels are gone except for the preview and radio ID. When I resend the signal I get my channels and weather back but lose them after turning the car off again. I have called xm technical support and they say it is a GM issue, when I bring it to my dealer they say that it is on XM's end. Also I have had the nav system firmware updated twice for other various issues. Any suggestions.