How Does Keyless Entry Work on Cars? | The Signal Behind The Click

Keyless entry unlocks a car when a radio signal from your key fob matches the code stored in the vehicle’s receiver.

That satisfying click when you grab the door handle isn’t magic, and it isn’t just a button. Keyless entry is a short-range radio conversation between your key fob and the car, designed to verify you’re nearby—and, for keyless start, that you’re inside. Understanding the handshake matters because it explains both the convenience and the real security risks every owner should know.

What Exactly Is Keyless Entry?

Keyless entry is a wireless access system. Instead of turning a physical key in the driver’s door lock, your fob or smart key sends a coded radio signal to antennas and receivers mounted in the vehicle. The car unlocks only if that code and proximity check match what its logic module expects.

There are two distinct flavors, and the difference matters:

• Remote Keyless Entry (RKE): You press a button on the fob. That press transmits a coded RF signal the car’s receiver decodes, which locks or unlocks the doors or pops the trunk.
• Passive Keyless Entry (PKE): You just grab the door handle or walk up to the car. The vehicle and fob perform a proximity and challenge-response check automatically, with no button press needed.

The Radio Handshake: How The Car Knows It’s You

When you press the fob button (RKE) or touch the handle (PKE), here’s the sequence that plays out in milliseconds:

1. The fob transmits. It sends a coded radio message containing an identifier and a command—unlock, lock, or release trunk.
2. The receiver verifies. The vehicle’s antennas capture the message and check it against stored logic, often using a rolling code method so the same code isn’t reused twice.
3. The action fires. If the code is valid, the car unlocks. For keyless start, the system performs an additional check—it verifies the fob is inside the cabin before the start/stop button will enable the ignition.

This two-channel setup is why a dead fob battery can still let you start the car if you hold the fob near the start button—the car can sometimes read the fob’s proximity chip even when its main transmitter is weak. If the fob battery is fully dead, though, the system may not work normally, and vehicle manuals typically provide an emergency backup procedure that varies by model. Kia’s owner manual pages, for instance, walk Seltos owners through backup entry and starting steps specific to that car.

Is Keyless Entry Safe From Theft?

Mostly, but not perfectly. The big threat in recent years is relay theft, which targets passive systems. Two attackers work as a pair: one stands near your front door with a relay device that captures your fob’s signal, and the other stands by your car. The relay extends the fob’s reach, fooling the car into thinking the fob is right next to it—which unlocks and, on keyless-start cars, lets the thief drive away. Encryption helps, but sources note it does not fully stop relay attacks on some models.

Practical defenses are simple: keep your fob in a metal-lined signal-blocking pouch (a Faraday bag) at home, or store it in a metal box. At night, keep the fob as far from the front door as possible.

There’s also a lesser-known safety angle. NHTSA documents note a genuine risk if a remote transmitter malfunction causes the engine to start while the car sits in an enclosed area like a garage—carbon monoxide can build up quickly and seep into the house. NHTSA’s interpretation of Federal Motor Vehicle Safety Standard No. 114 also confirms the key-locking system requirements for vehicles with automatic transmissions and a park position, and recall bulletins show some remote-start and keyless systems have been subject to malfunction-related safety recalls. If your fob or remote-start system ever behaves erratically, treat it as a repair priority, not an annoyance.

If you’re shopping for a system to add keyless convenience to an older vehicle—or want to compare aftermarket options against factory setups—our tested roundup of the best auto keyless entry systems covers the models worth your money.

Frequency and Compatibility: Why It’s Not Universal

Keyless entry is not one-size-fits-all. Here’s the breakdown:

The practical takeaway: a keyless fob isn’t universal across countries or even across models from the same brand. If you import a car or relocate, expect the keyless system to need a reflash or replacement—and never assume a fob from one vehicle will work on another.

When purchasing a used car with keyless entry, verify that the fob(s) match and that the system has no open recalls. NHTSA’s recall database is searchable by VIN, and it’s worth the two minutes to check. If a system has a history of malfunction-related recalls, you want to know before you hand over money.