Quentin W

So as mentioned in the past post, I have had the same problem. The only thing different about whats going on with yours is, I have replaced the harness twice, and then removed the mute wire from the 3rd harness. Also I don't have a blue-tooth device so there is nothing connect on that end. I haven't used OnStar since 2005 which is way before this head unit was even invented. I have swapped the head unit out twice and also swapped out the steering wheel control module twice and not running it at all on the third unit and still it goes into ATT or Mute depending on which one I have selected (-20