An MIT Alumni Association Publication

Can I Detect My Car's Keyless Remote If I Don't Know Where It Is?

  • Kate Repantis
  • 5

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Guest Post from the Ask an Engineer series, published by MIT’s School of Engineering

Maybe—if it’s the right type of remote and you have plenty of time and technical know-how (but don’t get your hopes up)…

So you’ve lost your car keys again. You’re sure they’re in your house, but you’ve already checked between your couch cushions and on top of the fridge, and you can’t find them anywhere. You have a keyless remote that seems to communicate with your car, and you wonder if maybe there’s a way to get it to communicate with you and tell you where it is. “In theory, it is possible,” says Phillip Nadeau, a Ph.D. candidate in electrical engineering and computer science, “but it depends on the type of remote-entry system we’re talking about. And even then, it could be tough depending on the manufacturer and technology used.”

There are two main types of keyless remotes—Remote Keyless Entry (RKE), and Passive Keyless Entry (PKE)—that work in different ways. RKE devices send a radio signal to your car only when you press a button on the remote. “These devices are generally only equipped with a transmitter,” explains Nadeau. Unfortunately, this means there’s no way to call the remote. It’s as unable to hear you as a skeleton key.

If you have a PKE remote, your odds are better. PKE devices don’t require you to push buttons to lock or unlock your car. “The car sends a signal that simultaneously powers the remote and asks for a valid authentication code to unlock the car,” explains Nadeau. This is essentially the same technology RFID card readers use to give you access to a building without you having to pull your ID card out of your pocket. Unlike a RKE device, a PKE remote has both a transmitter and a receiver, which would allow it to hear you call it with specialized radio equipment—you’re just pretending to be your car! In theory, you could custom-build a device that functions as a radio transmitter and receiver, recording the signal from your car, re-transmitting it, and listening for a response from your keys. This is not an easy or inexpensive solution, but if you have the technical know-how to construct such a device, it should work…

As long as you have a lot of time on your hands, says Nadeau. “The interrogator must be within a few feet the remote to elicit a response.” This proximity restriction is useful most of the time—if PKE remotes had a long range, people could steal the car right out of your driveway while the keys sit safely inside your house! But, it also means that you’re going to have to cover every square inch of your house with your equipment to find your keys. So, you might as well save the time and expense of building some complicated radio equipment and keep looking for your keys the old-fashioned way: going back and pawing through that junk drawer one more time.

Authored by Aaron W. Johnson, a PhD candidate in aeronautics and astronautics. Thanks to Suzan Atkinson-Haverty from Fitchburg, Massachusetts, for this question.Visit the MIT School of Engineering’s Ask an Engineer site for answers to more of your questions. 

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Cinderella sabangan

Wed, 09/06/2017 7:41am

How much and where to order the replacement of my key less remote for my eco drive


Thu, 10/19/2017 6:44pm

Could the signal be picked up on something as simple as an AM/FM radio? I remember hearing a chirping from an alarm clock radio every time I used my TV remote. Could a radio hear a similar chirp from a lost key fob if it were close enough to it? Forgive me if that's two different technologies, just trying to find a lost key fob. lol


Sat, 09/09/2017 3:42pm

It depends on where you live, but in SF, it's like $600 if you can't get you're car to the dealership, and even then it is about $300. That is the price for a smart car key, which in theory is inexpensive. The best option, is to order a key for your car online, and then get it cut, and programed separately.

In reply to by Cinderella sabangan

Alan Wu

Fri, 08/21/2020 11:10am

One practical precaution is to attach something like the Tile transponder to your keyfob. This add-on gadget is designed to respond audibly and virtually to a request from your cellphone, specifically to help people find lost items.

Alan Wu

Fri, 08/21/2020 11:21am

There have been media reports in the past 5 years, of thieves using special-purpose radio relay amplifiers to carry signals between keyfobs and locked cars which would normally be out of range. This basically fools the car into behaving as if the keyfob were only a few feet distant, while it actually was inside a house, apartment, or office. The thief could then easily open and rifle through the car, without setting off any alarms. The car could also be started, and driven off to some more-isolated location, where it could be stripped of parts.