Vehicle smart key: how does it work?

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If you’re thinking that this is an article about keys that can surf the Internet or make phone calls, you’re not quite right. But that doesn’t make these little devices that enable you to unlock your doors and start your vehicle without the use of a physical key any less innovative.

Also referred to as proximity keys or simply key fobs/remotes — each brand has a different name for their specific systems — smart keys have been around since the 1990s, although they were a feature found primarily on high-end luxury automobiles at the time.

How does it work?

BMW Comfort Access System

The smart key uses radio waves to “talk” to the matching vehicle containing embedded antennas that identify and confirm its presence. On some models, like newer BMWs (Comfort Access), when the key comes within 1.5 metres of the driver’s car, the door automatically locks or unlocks with a touch of the door handle. In the case of the above image, the tailgate lifts by waving a foot underneath the rear bumper.

Once inside, simply pressing the ignition button, usually located next to the steering column, starts the vehicle. Some smart keys, like those from BMW, can also store individual user settings so the seat, mirrors, steering wheel and even audio preferences are automatically adjusted by pressing a single button.

Honda engine start button


Rather than a smart key sending out the same frequency signal over and over, which would affect all the makes and models utilizing the same key, not to mention make it easier for tech-savvy thieves to steal cars, smart keys broadcast a different encrypted signal every time you unlock a door or remotely pop the trunk.

A computer chip located inside the car is responsible for receiving the signal and prompting a new frequency to be generated. Of course, nothing is foolproof, and manufacturers are constantly working at making their technology more secure.


opening car door

The most obvious plus of a smart key system is convenience. You don’t have to be holding the key in your hand to enjoy the features, and many people love the fact that they can keep it in their pocket or bag without having to reach in and dig around before getting into vehicle.


By the same token, there have been instances (writing from personal experience) where a driver hands a car over to another user and walks away, forgetting that the smart key is still on his or her person.

BMW emergency key

On models that don’t have an automatic proximity unlock function, if the battery in the fob dies, opening a locked door can be tricky. Luckily, almost all fobs should have a small metal key hidden inside that can be used to unlock the driver’s door via a keyhole often concealed underneath a removable plastic cap near the door handle.

To get a better visual of a smart key in action, here is a video illustrating the Intelligent Key system on the Infiniti Q50. 

Posted by Benjamin Yong

Benjamin Yong is a freelance journalist and communications professional living in Richmond, B.C. He is often found writing about cars and the auto industry, amongst other things, or driving around in his work-in-progress 1990 Mazda MX-5. Twitter: @b_yong Instagram: @popuplights