US Patent 7683764 Automatic locking failsafe for vehicles with passive keys

A method of unlocking a vehicle, which includes initiating an auto-lock command, searching an area surrounding the vehicle for a valid key fob, and sending a normal request from interior antenna if a valid key fob is not found. The method further includes sending a wide area request from an interior antenna if the valid key fob is not found from the normal request. The method includes locking the doors if the valid key fob is not found. The method provides a warning and does not lock the doors if the valid key fob is found.