How to Program a Key Fob

How to Program a Key Fob
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Key fobs are little pieces of technology that add huge convenience to your life. Parked in total darkness? No worries, the key fob can unlock the door when you touch the handle. Knowing how to program a key fob comes in handy for several situations you might encounter, so follow along for step-by-step instructions.

Why program a car key?

You probably have an idea of why you might need car key programming. It’s not that the program simply slips out of the fob, or the programming goes bad over time. Most likely the need for key fob programming is due to damage to the key, or a misplaced key fob that was replaced by an unprogrammed replacement (think of this as a digital version of a blank key). Maybe you bought an unprogrammed backup key, or the battery died in your primary and it lost the sync with your car, or your teenage driver needs their own key. Whatever the reason, you can usually reprogram the key fob yourself in just a few steps.

How to program a car key

The exact steps will vary with your make and model of vehicle. Reprogramming usually consists of a series of key fob button presses, sometimes including mechanical key operation or other involvement with the vehicle. Your model might need the unlock button pressed five times in a row, or several lock/unlock sequences followed by turning on the car.

In order to understand programming a key fob, let’s first look at how the key fob normally works. Press a button and the key fob transmits a radio frequency signal to the vehicle. Think of it as a simplified walkie-talkie system, but instead of transmitting dad jokes, it sends a short bit of data to unlock the car. This isn’t just on the right frequency, it’s also encrypted to prevent theft. The vehicle decrypts the message, verifies that it’s a valid command, then takes the appropriate action to lock, unlock, open the trunk and so on.

But before you attempt to manually reprogram your key fob, there are a couple of things to check.

Check the fob’s battery

If you bought a new primary or backup fob without a battery, or suspect that your current key fob’s battery has failed, start with that simple task to make the rest of these steps easier. Key fob batteries cost just a few dollars, while replacement key fobs from third-party sellers are easily over $100 before paying for programming.

Most key fobs contain a mechanical key that you can pull from the fob to allow access to the vehicle even when the battery has completely drained. For many manufacturers, this key also acts as the only tool you need to open the key fob. First, completely remove the mechanical key from the key fob. Then place the key partially back into the fob, near the center between the two halves of the fob. With a twisting motion, you turn the key like it’s in a lock, prying the two halves of the fob apart.

Continue until the fob pops in half, and you should be able to see the button-size battery. The battery slides out, and the replacement drops into place. Snap the key fob back together, replace the mechanical key, and this part is done. If your key fob wasn’t working at all, this may be the only fix needed.

Check your manual

If a new battery doesn’t resolve your key fob issue, it’s time to look at programming. Fear not, this isn’t like coding in Python, but just a series of buttons you have to press in order to get the vehicle and fob to understand there is a connection issue and to resync. This information can be found in some owner’s or repair manuals, but not all. For instance, Toyota’s owner’s manuals are usually unhelpful:

“If communication between the electronic key and vehicle is interrupted, the smart key system and wireless remote control cannot be used.”

Thanks, Toyota. Scion is similar, basically saying, “Don’t lose your keys.”

Have a look at how to program a car key for your specific model by searching online, and check out YouTube as it’s a great help with the visuals. Instructions for programming your key fob should look something like this example for a Cadillac STS.

  1. Turn the vehicle off.
  2. Place the new key fob into the transmitter pocket, located in the center console.
  3. Insert the mechanical key into the door lock cylinder in the driver’s door.
  4. Turn the key to the unlock position five times within five seconds.
  5. The driver information center displays “OFF/ACC TO LEARN.”
  6. Press “ACC” on the ignition switch.
  7. The driver information center displays “WAIT 10 MINUTES” and counts down to zero.

How to reprogram an ignition key fob

If your Google-fu skills are lacking, or no one really bothered to post your specific model on the interwebs yet, you can still give these generic instructions a try. These will work for some cars, but definitely not all. At worst, all you’ll end up with is locked doors and a key in your hand.

  1. Insert your original, programmed key into the ignition and start the vehicle.
  2. Turn the key to “off” and remove it from the ignition.
  3. Insert your new key to be programmed, and turn it to “on” within 10 seconds of removing the original key.
  4. Wait for the security light to turn off, indicating the key has been programmed. If your vehicle does not have a security light, wait at least 10 minutes before shutting it off to be sure the key has been programmed.

Alternative instructions to try:

  1. Get into the driver’s seat and close all the doors.
  2. Insert the key and turn it to “ACC.”
  3. Wait at least 10 minutes, then switch to “off” and remove the key.
  4. Repeat above steps 2 and 3 a total of three times. Once you finish the third round, the key should be programmed.

How to program a push-button start key fob

Push-button start is a great feature, except when you need to program the key fob. With no ignition lock or port in which to insert a key, this gets a little tricky. Fear not, we’ve got you covered with these steps that are applicable to many vehicles, but not all.

  1. Get into the driver’s seat with your key fob, and close all the doors.
  2. With your foot off the brake, press the “start/stop” button 15 times in rapid one- to two-second intervals.
  3. Immediately after the 15th press, hit the lock button on the key fob. The doors should lock, indicating the successful programming. If not, try this sequence again to make sure it wasn’t a timing error.

What if key fob reprogramming doesn’t work?

If you attempted the above key fob reprogramming steps and didn’t see results, you might be out of luck with DIY programming. It’s not that your vehicle is bad or that you made a poor buying decision, it’s just that with the wide variety of vehicles and manufacturers on the road, your specific reprogramming requirements are different. Embrace your uniqueness, then see your additional options below.

Contact a locksmith or mechanic

If you don’t trust your DIY skills, but also don’t love dealership prices, a locksmith or third-party mechanic might be your key to a working fob. Local locksmith chains and some independent shops can quickly and easily program a key fob. If you need a replacement fob, call around for the best deal, as prices will vary—usually around $40 to $150 depending on the model. If your car is a decade or so old, look for cheapo third-party key fobs with good reviews for under $10. Expect professional programming to cost another $50 on top of that. That’s a lot more than the free DIY route, but there’s peace of mind that a professional performed the task, and they can often come to you, rather than you paying for an expensive tow.

Contact your dealer

If you need key fob reprogramming, and just want it done, few places beat the dealership service center for the ability to complete any task on their brand of cars. You can easily order the right key fob and have it programmed the same day it arrives. It sounds great, but know that this is the most expensive route. A call to a local dealership for a hypothetical 2020 Toyota Avalon needing just key fob programming resulted in a quote of $120 and about an hour’s time. While this is a larger out-of-pocket expense, it takes all of the hassle out of the process, and it’s backed by the manufacturer’s warranty. If you value peace of mind ahead of your wallet, this could be the route for you.

Don’t hit the panic button

Key fob programming doesn’t have to lock you out like you’ve entered the wrong Netflix password too many times. You have three main options for getting back into your vehicle and hitting the road. Decide which option above is best for you and go get that key fob some new instructions.


About Bumper

At Bumper, we are on a mission to bring vehicle history reports and ownership up to speed with modern times. A vehicle is one of the most expensive purchases you'll likely make, and you deserve to have access to the same tools and information the pros use to make the right decisions.

Disclaimer: The above is solely intended for informational purposes and in no way constitutes legal advice or specific recommendations.