hello iam travelking i have the same problem. i have an 2007 ford edge with the navigation/ subwoofer. i was told to remove the seat belt and the rear panels in the back and that the harness to the subwoofer is worn out and has to be changed. i havent done anything to mines as of yet. the bass goes of and on. for a while, it works better when the stereo i on for long periods of time. hope this is of sime help to you. if you learn more pls tell me.