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.