I went out to my 2013 ATS today and it is dead. Key FOB won't open doors. I used the manual key to get in and no lights come on or the GPS Cadillac logo does not come on. It is completely dead. This this how a dead battery acts? I had no warning. It seemed to start and run fine a couple of days ago. It justs seems if it were the battery there would be some sort of warning. Anyone else had this?