How to Fix a Broken Car Key Fob

As an amazon associate motorhills.com earns from qualifying purchases.
Broken-car-key-fob

A broken key fob is a quick way to ruin your plans for the day. If you can’t even get in your car, how are you supposed to run errands or get to work? You need a fast solution and don’t have time to waste.

If your key fob isn’t working right, the lock/unlock functions and other features won’t work. What’s worse, if there is no power going to the transponder, your vehicle might not start.

The most common issue with a key fob is the battery going bad. Replacing the key fob battery is the most common fix for a key fob. Some batteries are easy to swap out, other ones need to be de-soldered. It all depends on the year, make, and model. If the housing is bad, oftentimes, replacement housing can easily be purchased via Amazon or eBay.

In our guide, we’ll explain everything you need to know about car key fobs. We’ll tell you how they work, why they might be broken, and how to fix anything that’s wrong with them.

First, let’s explain how you can get into your car and start it, even with a broken key fob.

Emergency: Getting into Your Car with a Broken Key Fob

Before diving into the juicy stuff, we want to walk you through two situations at the top of this article. This section is all about getting into your car even with a broken key fob, and the next section will show you how to start your car.

When you press the unlock button on your key and it doesn’t work, you’re not stranded. There’s still a way into your car.

Examine the back and bottom of your key fob. It varies depending on your car’s make and model, but there’s almost always a hidden key in there. If you see a little switch or latch, figure out how to disengage it.

When the latch is disengaged and the neighboring plastic is pulled, you’ll pull out a mechanical key and probably feel like King Arthur pulling out the sword Excalibur when you do so.

This key is cut for your specific car. Throw it in the key latch in your door and turn it like an old-school key.

Sword-in-the-stone
Removing the hidden physical key from the key fob

Wait, There’s No Key Latch in My Car’s Door

In some cars, there’s not a noticeable key latch. You’ll have to locate a little strip of trim near the handle of your door and pull it back.

Be warned: Pulling back this trim has a risk of scratching your car’s paint. In that case, you’ll need to use one of our suggested scratch removers.

With the trim pulled back, the latch should be revealed so you can let yourself into the car.

Emergency: Starting Your Push-to-Start Car with a Broken Car Key Fob

Now you’re sitting in the car with a mechanical key in your hand, a broken fob, and a perplexed look on your face. There’s a push-to-start button on your dash, but it won’t work without a live key fob.

Car designers are smarter than we give them credit. There’s a hidden slot somewhere that will help us in this tricky situation.

You might have to refer to your owner’s manual or start really looking at things around your car. Somewhere there will be a slot to put your dead key fob in and start the car. Where might it be?

  • On the wall of your glove box. After opening the glove box, look for a slot on the exposed left wall.
  • Under a plastic panel to the left or right of your steering wheel. You might find a key logo on a plastic piece near your steering wheel. It can either be removed or the fob can be held against it to start your vehicle.
  • Directly under the push-to-start button. Some cars have a slot right under the start/stop button that reads “keyless”. Your dead fob can be inserted into this area to start your engines.
  • In the cup holder. You might have to remove the rubber liner at the bottom of your cup holder to reveal a key symbol.
  • Under the liner of your center console. Equally, you might have a hidden key symbol under the liner of your center console. Leave your keys on the symbol and press the start/stop button.
  • Push the start/stop button with your fob. Using your fob to press the button might be the solution to your problem. A lot of Japanese cars use this method.
  • A door above the console. If there’s a plastic flap above your console, that might be the hiding spot for this slot. Carefully pry the door back and reveal the underbelly.
  • Under the start-stop button. Pulling away the plastic face of this button reveals the slot.

Try out all of these hiding spots. When your car starts, you can now safely drive home, to a dealership, or to a locksmith to get your key fixed.

With these emergency solutions out of the way, we can get this article started.

Key-fob-being-inserted-into-keyhole-near-start-button
Some vehicles have a key fob slot under the start button, in case the key fob battery is dead. Note, not all vehicles have this.

What’s a Key Fob?

A key fob is an electrical device that gives you access to your car without any physical interaction of a key. Remember the old days? You would have to hold your mechanical key, twist it in the door, then put it in the ignition and turn it again.

How lame is that? In today’s age, a majority of modern cars on the market use a key fob. You use it to remotely unlock your doors and you might be able to start your car without turning a mechanical key at all.

How Does a Car Key Fob Work?

As modern as the key fob is, it uses a pretty old technology: radio. Each fob has a little radio transmitter built into it.

The transmitter is programmed and coded to a certain frequency and paired to a specific receiver. The receiver is found in your car.

When the transmitter and receiver are within range, they can start to talk and interact with one another. What does this look like? Pressing the unlock button and having your car doors unlock.

Wireless-key-fob-range

The range is typically less than 50 feet. For starting your car, most cars will require the key to be within the vehicle itself, which requires good proximity.

Without a key fob (or mechanical key from the fob), you can’t open doors or start your vehicle. A broken fob takes all the convenience out of this process by requiring a mechanical interaction with different parts of your car.

The Nerdy Part of the Programming

So, there are only so many frequencies that a key can use — how come your key fob doesn’t unlock random cars in the parking lot? It’s thanks to the nerdy part of the programming inside the key.

Every time you unlock your car, the code key changes. This means that a thief can’t wait around your car with an interceptor and steal your unlock code after you unlock your vehicle.

This level of security is also why the keys are more difficult to replace than you might think.

Parts of a Key Fob

Crack your key open and what do you find? It’s almost always the same roundup of parts.

The Housing

The housing is the plastic shell around your fob. It’s almost always two injection-molded pieces, and you should see a seam along the sides. When you pry this seam apart, you’ll open the fob and show all the fun internal components.

The main job of this shell is to protect the electronics inside.

Key-fob-inside-components
Inside a key fob

Rubber-Padded Buttons

The buttons get assembled in the housing and push on the circuit board underneath. The board is programmed so that depressing a button has a certain action.

For example, hitting the lock button will result in your ‘car doors’ locking. These buttons are replaceable and interchangeable if your buttons wear down or start to fall apart.

Circuit Board

The circuit board is the brain and heart of the operation. This is the green piece of electronics with copper-colored circuits running all over. This is also where the tiny, short-range radio transmitter is hidden.

Be careful when opening up the key fob especially when using a hard edge like a screwdriver to pry it open. I’ve had to fix a circuit board with tiny components torn off the circuit board under the microscope due to someone trying to pry it open quickly with a flat-head screwdriver.

It took me at least an hour and steady hands but I was able to fix it, otherwise, the person who brought it to me would’ve needed to spend several hundred dollars getting a replacement from the dealership.

If this board is damaged, the key fob won’t work correctly.

Key Ring

Some key fobs have an independent key ring that’s assembled with the fob. Others have a ring molded into the shell.

If you pop open your fob and the ring falls out, don’t panic. You can put it back in place and close the shell.

Battery

Another big player in a key fob is the battery. In almost every fob, you’ll find a CR-series battery. C stands for “Lithium” (don’t ask us why), and R stands for “Round”.

If you look closely at the positive side of the battery, you should see an inscription of which CR-series battery it is. A CR2016 doesn’t work in a battery that requires a CR2450.

This battery is the sole power provider of your key fob. If the battery is dead, broken, or missing, your key fob will have no electrical power. Basically, the fob is useless at that point.

If it’s a removable one, then it should be fairly easy to replace it and get your key fob working again.

Key-fob-circuit-board-battery
CR-type battery housed inside the key fob

However, there are some that are soldered into the circuit board inside. For example, BMWs that use a rechargeable CR-type battery but with two prongs soldered into the board, a special battery will have to be ordered and it’ll take some soldering to replace it.

Spoiler alert: you want to cross your fingers that it’s just a dead battery.

Physical Key Switch

Somewhere in your fob will probably be a physical key. When you crack open your fob, you’ll undoubtedly find it.

This physical key is the one we were talking about in our intro sections: it will give you access to your car’s locks so you can get into a vehicle even with a dead key fob.

The Reasons Why Your Key Fob is Broken

Okay, so now you know what the fob is and the parts that go into it. That still doesn’t fix your problem at hand. This was necessary because you need to know the right terms and ideas before we can start talking about why your fob is broken.

Here are some of the top reasons why your key fob is broken or not working. In a later section, we’ll describe how to fix each issue.

Dead Car Battery

Before blaming the fob, realize that it could be thanks to a dead car battery. Not the fob battery, but the big one under your car’s hood.

If your car’s battery is dead, doors won’t automatically unlock with your fob’s buttons. The car won’t ignite when you press the push-to-start which might also cause you to blame the fob.

Before getting too mad at your fob, troubleshoot your car’s battery.

Dead-car-battery

Dead Fob Battery

As we mentioned, a fob is only as good as the battery inside. If the battery is busted, then the fob is just a fancy piece of plastic.

Without power being supplied to the electrical circuit board, the electrical magic can’t happen when you hit the buttons.

Broken Circuit Board

If the circuit board is dead, broken, or damaged in any way, the fob could act weird or not work at all. This board is responsible for transporting electrical signals around and activating responses based on the buttons you press.

Something as simple as getting your key fob wet could result in a broken circuit board.

Physical Damage

Maybe the damage is just aesthetic but it’s driving you crazy. Chips, marring, and broken pieces on your fob are definitely less than desirable.

This is one of the better options when it comes to damage to your fob.

No Programming

If your fob doesn’t have the nerdy programming we talked about earlier, it won’t work with your car. This is a way of tethering your specific fob to your vehicle.

Think of it like ‘Bluetooth pairing a device to your phone.’ There is oftentimes a specific procedure on how to pair a ‘virginized’ or ‘non-programmed’ key to your vehicle.

Key-programming-in-car

If there’s no programming, the fob could work perfectly fine but not send the radio transmission to your car’s receiver. The result? A non-functioning key fob.

Dirty Contacts on the Circuit Board

There are things called contacts in your fob’s circuit board. When a button is pressed, the contact is interacted with which starts the process. A dirty contact won’t read the incoming signal as a button is depressed.

Copy of a Copy of a Copy

If you’re looking specifically at the mechanical key portion of your key fob, it might be an issue of copies. Every time a copy is made of your key, the new key is a little less accurate.

After enough copies, the final key will be so far from the original that it won’t work in your vehicle.

It’s always a good idea to make copies from the master key. This minimizes the discrepancy between all of your keys.

Car-key-copy
Professional machine making a new key

Who Can Fix Your Broken Car Key Fob?

When it comes to fixing a key fob, there are three places you can go:

  • A dealership
  • A locksmith
  • Your workshop

There are some issues you can’t fix on your own, but we always suggest starting there. Some issues with your fob might only take five minutes to fix. In our opinion, it’s just not worth wasting time dealing with a locksmith or car dealer.

Price for Repairing a Key Fob

Price Through a Locksmith

A locksmith will charge less than a dealership, but it will cost more than a DIY repair. This value values wildly based on your location and what kind of car you have.

A locksmith will usually have a good OBII scanner and various keys and key fobs that are blank ready to be cut and programmed.

Key-locksmith

They won’t carry every possible key in the world made for every single year, make, and model but will have quite often the most in-demand ones at their disposal.

If it will need programming, that’s where their OBDII scanner will come in to finish the pairing of the key to the VIN of your vehicle.

In general, you can expect to pay around $200.

Price Through a Dealership

Dealerships mark up the cost of a new key fob, but what else is new. If you choose to get a replacement through a dealership, expect to pay upwards of $350.

The nicer your car is, the more expensive the replacement it.

In addition, you have to hope that the dealership has spare parts in their store. Otherwise, you’ll have to wait days or weeks to get a new pair of keys.

It’s worth mentioning that certain car key fob replacements can only be done through a dealership. There will be special programming that a locksmith can’t duplicate, and you can’t handle on your own.

Price Through DIY

A DIY repair is going to be the cheapest option. If you’re really lucky, you can get it done for under $4. For a full replacement, expect to pay around $20 in parts.

Troubleshooting the Problem

We’re about to give you some solutions that are contingent on the problem you’re having. Take a second and troubleshoot your key. Crack it open and take a look at the internal pieces before moving to the next section.

key-locksmith-keys

How to Fix a Broken Car Key Fob

Here’s the part you’ve been waiting for: how to fix a broken car key fob. There are a number of root causes for a broken fob, so we’ll break this down into sections for you. Each section will highlight one specific reason how your fob isn’t working and how to fix it.

Fixing a Dead Fob Battery

A dead fob battery is the quickest, easiest, and cheapest solution on this list.

Before removing the battery from the pack in the fob, take a look at its orientation. In most cases, the positive terminal will be sticking up towards you. You’ll have to remember this for when you put a new battery in.

Take out the dead battery. It will come out either by flipping over the fob and rattling it, or using a thin flathead screwdriver.

Car-key-battery-fob

Get really close to the battery and see if you can read the text on the positive face. This will help you identify what type of battery you need to replace it with.

If the text is rubbed off, don’t sweat it. You can hit up the internet and type in your car’s make, model, and see what key fob battery should be used to replace.

Alternatively, grab that battery and run over to your nearest auto part shop. You can either show it to one of the people working there or head over to the fob battery aisle and compare the size between your battery and the ones for sale.

Places like Walmart also sell these batteries since they’re not exclusively used in car fobs.

When you get a new one, throw it in the fob (remember the correct orientation), seal up the fob shell, and try it out.

It’d be a good idea to grab a handful of these CR batteries as backups in case this happens again.

CR-Lithium batteries
CR-Lithium batteries

Fixing a Missing Broken Key Ring Attachment

If the keyring is broken from your fob, there’s no sensible way to carry it around with the rest of your keys. Duct tape will only take you so far and it’s doing a disservice to the aesthetics of your fob.

The big problem is that the keyring is often built into the housing.

This process starts by opening your fob’s housing. The back of your fob might have a serial number which will come in handy in a second. If not, just remember your car’s make, model, and year.

Go on amazon and search for either the serial number or your car’s specifics. Tag long the phrase “key fob replacement”.

For example, if you drive a Lexus IS330, you can pick up this replacement:

Replacement Keyless Entry Remote Key Fob Cover for Lexus ES GS GX is LS LX RX

Replacement Keyless Entry Remote Key Fob Cover for Lexus ES GS GX is LS LX RX
Replacement Keyless Entry Remote Key Fob Cover for Lexus ES GS GX is LS LX RX

Wait a minute, where are the battery and circuit board and buttons? You don’t care about those things; you just care about that juicy keyring that’s molded into the shell.

All the working components from your current fob can easily be removed and transferred into this new housing. Sort of like a hermit crab.

Fixing Surface Damage to a Key Fob

Surface damage like scratches, scuffs, and chipped pieces is annoying but not mechanically or electrically damaging. The process follows the exact same path as the previous section about fixing a missing broken keyring attachment:

Take it apart, buy a new fob housing, and transfer over the electronics. If it’s just the buttons you want to replace, you can buy a set of replaceable buttons for certain keys.

If you can’t find button replacements, you’ll have to buy a brand new fob since most of the replacement housings only come with the shell.

Fixing a Mechanically or Electrically Broken Key Fob

This problem is the most tedious and expensive on our list. It essentially means that something is wrong with your circuit board.

If the board got wet, smashed, or electrocuted, then it’s often irreplaceable (just like that Beyoncé song).

You’ll have to buy a brand-new key and take it to a dealership or locksmith to have it reprogrammed. In some cases, you’ll need to buy the key from the dealership.

If you don’t care about using an OEM key, you can grab a programmable fob from amazon, for example like this one made for select GM models:

2 Replacement Keyless Entry Remote Start Car Key Fob for 22733524 KOBGT04A Malibu Cobalt G5 G6 Grand Prix Lacrosse Allure

2 Replacement Keyless Entry Remote Start Car Key Fob for 22733524 KOBGT04A Malibu Cobalt G5 G6 Grand Prix Lacrosse Allure
2 Replacement Keyless Entry Remote Start Car Key Fob for 22733524 KOBGT04A Malibu Cobalt G5 G6 Grand Prix Lacrosse Allure

The key fob costs around $8 each. You’ll be able to take this to a locksmith and have them program it.

Fixing Dirty Circuit Board Contacts

There might be dirt that can’t be seen by the naked eye on your circuit board’s contacts. As a reminder, these contacts interpret a physical pushing of a button into an electrical response of your car doors unlocking, for example.

Take apart your key and carefully grab the circuit board. Hold it from the sides with one hand during this process.

Inspect the circuit board (PCB) for any dust, debris, corrosion, and/or sand. Some residues are worse than others.

Circuit Board with a lot of different components (close-up shot)
Circuit Board with a lot of different components (close-up shot)

For example, severe corrosion will most likely not be easily fixed with a simple cleaning since component surfaces will be oftentimes be disintegrated or no longer properly soldered to the board.

Use Q-tips with some 99% isopropyl alcohol. Apply the 99% to the Q-tip, then rub it on each contact carefully.

In the end, you should have a number of Q-tips with some noticeable dirt on them. Put the key back together and give it a try.

Is a Key Fob Replacement Covered Under My Car’s Warranty?

If you have a bumper-to-bumper warranty, a fob replacement might be covered. Make sure you talk to your dealership to see what they can offer you.

If that’s the case, definitely cash in on this benefit and get a brand-new fob directly from the dealer for free.

Car-warranty-icon

Can You Reprogram a Key Fob on Your Own?

With a functioning key fob and a lot of luck, you can reprogram your new fob on your own. There are only certain cars that allow this to happen, so don’t get your hopes up. Still, it’s definitely worth a shot.

Grab your spare key fob that’s functional and your dummy key fob that hasn’t been programmed yet. Enter the car with both in your pocket.

  1. Use the live key to turn your car to the “On” position. Don’t turn on your engine, just give your vehicle power.

2. Hit the lock button on your live key then turn your car off. Repeat this process three times. Turn your car to the “On” position. If your car automatically makes a locking noise without you pressing anything, you’re in programming mode.

3. Within 5 seconds press the lock button on your live key. On your dummy key, hit the lock button within 5 seconds of hitting it on your live key.

This should program the dummy key to your car. Turn off your car, exit the vehicle, and try using the dummy key to unlock and start your vehicle. Keep the live key about 100 feet away so it doesn’t interfere.

*Note – This programming procedure may not work for your vehicle but is a common universal method to program a new ‘non-programmed key. You may find more information online on how to pair a key to your specific vehicle if the method is different.

If this doesn’t work, you’ll need to get a dealer or locksmith to program your key.

Car key fob in the 'on' position
Car key fob in the ‘on’ position

Life Hack: Use Your Spare Key to Make Another Spare

If you have one functional key fob, it’s easier to make spares at a locksmith. This saves you money and removes the hassle of working with a dealership.

Take your working key to a dealership and have them make a spare or two to have just in case.

Conclusion

You’re now an expert in key fobs. You just learned what they are, how they work, why they break, and how to fix them no matter what went wrong. For more car tutorials, check out the rest of our blog. Also, be sure to get the accessories and tools you need to be a happy car owner.

Your subscription could not be saved. Please try again.
Got it! Check your inbox for a confirmation email.

Sign up for Exclusive Car Tips

Get Access to Useful Automotive Tips from Motor Hills

Motor-Hills

Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

Leave a Comment