The behind-the-scenes mechanism that locks and unlocks your vehicle’s doors with the push of a button is the power door-lock actuator. Mounted inside the door, it includes an electric motor, gears and linkage, or a cable that extends or retracts to operate the lock. On many modern vehicles, the lock actuators are monitored by electronic controls (such as the body control module) that have to receive the correct antitheft code from a key fob transmitter before they’ll send electrical current to unlock the doors. Each door has its own power lock actuator, and the motor turns in one direction to lock the doors and the other to unlock them. The linkage typically has a hook on the end that moves the lock up or down, making it similar to having a permanently installed “Slim Jim.” Actuators can stop working or develop intermittent problems because electrical contacts or circuits wear out, dirt gums up the gears or the motor fails from long-term use.