I have an 09 Tribeca with 6 cd changer. All of a sudden the navigation system has gone dead. The temperature dials don't show readings but still can control the heat/ac. Nothing happens with the sound. The door open light still lights up and the AC button and the buttons on that row still light up. Airbag light also can come on. I don't know if it would be the panel as I don't know how that would keep the nav off. If it is a control unit or some type of motherboard I can replace it. Doesn't seem to be a fuse. Never intermittent. Always happens. Any help would be appreciated.