There can be numerous reasons for the door lock in your Ford Expedition to not work, but the most common reasons are the lock cylinder itself or the rod connecting it to the door latch. You can replace either of these components to fix the lock; replacing the lock cylinder means replacing the door handle as well on most models. Fixing the lock on the rear door of the Expedition is much like repairing the lock on a front door.
Raise the window all the way and disconnect the negative battery cable.
Detach the manual window crank, using a hooked tool or a rag, or pry off the electronic window controls with a trim stick, disconnecting the electrical connector.
Pry off all remaining trim bezels on the door panel and remove the panel's screws. Pry off the door panel with a large trim stick and pull the panel off the door.
Unsnap and detach the plastic clips attaching the lock cylinder and door handle to the latch rod by reaching through the door's access hole. If the problem is that the lock's latch rod is disconnected or broken, reconnect or replace it.
Remove the retaining nuts for the outside handle, using a small wrench, and remove the handle and lock cylinder if the cylinder is the problem.
Install the replacement handle and cylinder within the door and apply the mounting nuts.
Connect the latch rods to the door handle and the lock cylinder.
Reconnect the door trim panel with its clips and screws; then reconnect the trim bezels, window controls and the battery cable.
