If you've suddenly discovered that the key lock cylinder on your Buick Century is broken, replacing it is not a difficult task. You can buy a new lock cylinder at your local auto parts store and, with just a few tools, install the new unit using this guide.
Detach the black, negative battery cable with a wrench.
Unfasten the mounting screws from the upper and lower steering column using a Phillips screwdriver; remove the covers from the column.
Follow the wire attached to the key lock cylinder and disconnect the wire electrical connector by slightly lifting the lock tab with your finger or a standard screwdriver and pulling the plastic connector from the harness fitting.
Insert the key in the lock cylinder and turn the key to the "Start" position.
Insert a 1/16-inch Allen wrench or similar tool into the hole located on top of the lock cylinder housing assembly, and push the wrench to release the cylinder-retaining pin.
Pull the lock cylinder out of the lock cylinder housing assembly.
Position the new key lock cylinder next to the cylinder housing. Align the locking and positioning tabs of the new cylinder with the corresponding tab slots on the cylinder housing.
Push the new lock cylinder into the cylinder housing assembly. (On some models, you have to install the lock cylinder with the key in the Run position for the cylinder pin to lock correctly.)
Insert the key that came with the new unit into the new lock cylinder, and rotate the key in all the positions and back to the "Off" position.
Plug the new lock cylinder electrical connector to the wiring harness.
Place the covers on the steering column and tighten the mounting screws using the Phillips screwdriver.
Attach the black, negative battery cable with the wrench.
