The door lock or lock cylinder on a car or truck is a small metal cylinder you insert the vehicle's key into when you want to lock or unlock your door. Lock cylinders usually need to be replaced after a vehicle has been broken into. Often, a flat screwdriver will be inserted into the lock cylinder to break it open, which leaves the lock cylinder inoperable. Replacing a lock cylinder on a car or light truck is within the abilities of most mechanics, and can be accomplished with a few simple tools.
Make sure the glass window panel is fully raised.
Remove the manual window crank handle (if equipped), either by inserting a window crank removal tool between the crank and the door panels (GM vehicles), or removing the screw at the base of the handle that secures it to the regulator shaft.
Remove the screws that connect the armrest to the door panel. Remove the armrest.
Remove any exposed screws that connect the upholstered interior door panel to the steel door frame.
Remove the interior door panel. Most interior door panels are secured to the door frame using hidden plastic clips. Place a flat-blade screwdriver between the door panel and the door frame. Slide the screwdriver around the perimeter of the door panel until you hit one of the hidden clips. When you find one, pull straight out on the screwdriver to disengage it. Continue around the edge of the door panel until all the clips are disengaged.
Locate the door lock cylinder on the inside of the door. It will be located near the exterior door handle.
Disconnect the actuating rod from the door lock cylinder. In most cases, you will have to remove a small steel clip and pulling the actuating rod off the cylinder.
Remove the steel clip or nut that secures the lock cylinder to the door.
Remove the lock cylinder. At this point, you should be able to slide it out of the mounting hole in the door.
When replacing door locks, you must replace all of them including the boot and ignition lock, if you want one key to be able to open all the locks on the vehicle.