I have a '93 Cadillac. When you turn the key to start the car the doors lock. There is a little tab switch that goes up and down that you can unlock the door while the car is still running and when you turn off the key or put it in park while it is still running it automatically unlocks. But sence my car didn't start, There was just enough juice to lock the doors I guess. I could not unlock the door manually. But after I did get out of the car I checked each door. I could move the lock tab if I had something to give me leverage. It was very tight and hard to move. Got a new battery and solved the problem but still, I never ever thought about something like this happening.