I have a 2006 Avalanche which is in better than average shape with a working OnStar system that I hve a subscription to. This past week I went to use the phone feature and it did not work. Then I tried the other features and they did not work either. Contacted OnStar who could not connect with the truck and then informed me that I needed to return the truck to the dealership. I did so, but was informed that there will be a $60 diagnostic hook up fee in addition to any parts needed to fix the issue. I have also learned that the antenna could have come undone. Where is the connection for the antenna located and are there any pre "hook up" work that I can do to possibly save me $60 plus miscellaneous charges or parts along the way?