to diagnose. use key to lock doors. once locked, see which one will unlock by trying to open the door. if any of the doors open, the one that opens will be crook.
ie, i had a car come in last week. Using the remote, the doors would lock and then unlock straight away so really the car wouldn't lock. i used the key and they all stayed locked but when i went to open the left hand front door, it unlocked the rest of the car. problem was the left hand front door lock actuator.