How car central door locking system works?

From Nano to Benz you will find central locking system (some times called power door lock) in almost every car. You may be wondering what is a central locking, how it works.

Types of central door locking system

On the basis of Modus operandi of  central door locking system or power lock can be any or combination of the following two types:

  • Manual system: Power lock system allows to centrally locking all the doors of the car including tailgate from the driver’s gate by pressing a button manually.
  • Remote keyless system: Locking / unlocking of the doors can be done by a remote controller as well. Much like the way a television remote control works. By pressing a specified button on remote person can enter in to car without using a key.


Construction of central door locking system

Power lock is an electro mechanical system. We can divide the central door locking system to the following subsystems:

  • Remote controller: Remote controller is a small hand held battery operated device. Transmitter of the remote controller can produce unique coded infra red (IR) or radio frequency (RF) signals to ECM (Electronic Control Module) upon pressing the different buttons of it.
  • Electronic Control Module (ECM): ECM is the signal processing unit. It decides the amount of polarity of power to be supplied to different solenoid or motors of actuators upon receiving the IR or RF signals from remote controller.
  • Actuators: Locking / unlocking of power lock is actually happen by the actuators. These are placed in the doors. Following two types of actuators are used :

1.      Solenoid: Solenoid is an electromagnetic switch. It locks the doors when current passed in it by the ECM in one direction and unlock when the direction of current is reversed.

2.      Motor: In place of solenoid, DC motors could also be used as actuator. The rotary motion of the motor is converted to linear motion by means of rack and pinion mechanisms. Again by changing the directions of current rotation direction of motor is changed .Thus it locks for one direction of current decided by the ECM and unlocks for opposite direction.


Applications of power lock

Earlier the usage of power lock was limited to the passenger doors but nowadays all the doors, tailgate and fuel lid is controlled by central power lock.




Central locking system is an electromechanical system. Central locking system can be operated manually or by a remote key less system. From design point of view remote controller, ECM and actuators are the major subsystems of central locking system.

Shibashis Ghosh

Hi, I am Shibashis, a blogger by passion and engineer by profession. I have written most of the articles for For more than a decades i am closely associated with the engineering design/manufacturing simulation technologies.
Disclaimer: I work for Altair. is my personal blog. Although i have tried to put my neutral opinion while writing about different competitor's technologies, still i would like you to read the articles by keeping my background in mind.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.