Last night my 2007 HHR's horn went off in three short honks twice, then stopped. I went out to the carport and checked it, found nothing wrong except suddenly my key fob wouldn't work. At 6:00 this morning the alarm started blaring. Checked again, found nothing wrong. It did this 3 times and finally stopped. I changed the battery in the key fob between the second and third alarm honking. Any suggestions what is going on? TIA.