How Rolling Codes Work

When you press the lock or unlock button on your car key fob, it sends a rolling code to your car. This rolling code changes every time you press the button, making it very hard for thieves to copy and reuse the signal.

Although the codes look random, your car and key are actually synchronized so they both "know" what the next valid code should be. There are trillions of possible rolling codes, making it highly secure.

What Happens If You Press the Button Out of Range?

If you press your key fob when the car is too far away, the key moves to the next rolling code, but the car doesn't receive it. This might make you wonder: Won’t the key and car get out of sync?

To prevent this issue, cars have a buffer of about 256 codes ahead. This means:

If you press your key fob up to 255 times while out of range, the car will still recognize the next code when you're back in range.

But if you press the button more than 256 times out of range, the key and car become completely out of sync. In this case, the key will no longer work, and you'll need to reprogram it to sync it with the car again.

Why Your Key Might Not Work Sometimes

If your car key suddenly stops working, it might be because:

• Someone (like a child) pressed the button too many times while the car was out of range.
• Something was accidentally pressing the button repeatedly, like inside a bag or pocket.

The Cool (and Slightly Scary) Part

This system is an example of computers predicting the future—the car and key don’t just rely on a fixed number, but instead use an advanced algorithm to keep them synchronized.