The door lock cylinder is designed to secure the fuel door, preventing unauthorized access. This fuel door lock cylinder can experience wear over time, resulting in decreased functionality due to rust, excessive force applied while unlocking and locking the fuel door, attempted theft or vandalism. If the fuel door lock of your vehicle is difficult to open or close and your keys will not turn, then the cylinder may be damaged or broken. You can locate it on the side of vehicle, in the fuel door.