What To Do When Your Car’s Key Fob Doesn’t Work

Modern car key fobs are extremely convenient, that is until they go on the fritz. When they stop working, you can be left unable to lock and unlock the doors, or even start the engine, without physically inserting a key. Plus a busted key fob can be expensive to replace.

If your car’s key fob has stopped working, you've come to the right place. Here, we'll guide you through a series of simple, actionable DIY steps to get your fob back up and running.

1. Replace the Battery

A dead battery is the most common reason a key fob stops functioning. Fortunately, batteries for key fobs are relatively cheap and easy to replace.

Start by opening the key fob. Most have a seam where its two halves meet; use a small flathead screwdriver or thin coin to gently pry them apart. Once the key fob is open, you should find a disc-shaped battery inside. Note the battery's position before removing it, as this will help you insert the new one correctly.

Next, be sure to replace your battery with the exact same type. The type is usually indicated by a series of letters and numbers stamped on one side. Common versions include CR2032, CR2025 and CR2450.

Finally, place the new battery into the key fob in the same position as the old one and ensure it is seated properly before snapping the fob back together.

2. Verify the Signal

If you’ve replaced the battery and the key fob still isn’t working, the next step is to verify whether it’s transmitting a signal. Key fobs communicate with your vehicle through coded radio frequency (RF) signals, and if those are nonexistent or weak, the car won't respond.

Most auto parts stores offer key fob testers designed for this purpose. Typically costing around $25, they are straightforward to use: simply place your key fob near the tester and press one of the buttons. The tester will then indicate whether a signal is being transmitted and its relative strength.

If your key fob isn’t transmitting a signal, it will likely need to be replaced. But before you order a new key fob, check inside the old one for a correctable issue like a loose connection you can gently push back into place.

If you find corrosion (typically a white or greenish residue), clean it off with a dab of isopropyl alcohol on a cotton swab. With any luck, these simple fixes will save you the cost of replacement.

3. Reprogram the Key Fob

If you’ve replaced the key fob battery and verified its signal and it’s still not working, try reprogramming it. Key fobs sometimes lose synchronization with the vehicle, especially after the battery has been replaced. Reprogramming can restore that connection.

Reprogramming key fobs varies between different makes and models, so consult your owner’s manual for specific instructions. Generally, the process involves these basic steps:

1. Most key fobs contain a hidden physical key that can be used to unlock the doors or start the car manually. You’ll need this physical key for the next three steps. Look for a small button or latch on the key fob to release the emergency key.

1. Enter programming mode by inserting the key into the ignition and turning it to the “On” position (without starting the engine). Some vehicles require that you cycle between “On” and “Off” several times or press a sequence of buttons.
2. Once the car is in programming mode, press a button on the key fob to reconnect it. You may need to hold the button for a few seconds until you see a response, such as the doors locking and unlocking or the horn sounding.
3. Exit programming mode by switching the ignition off.

With these easy steps you should be able to bring your key fob back to life. If not you’ll have to order a replacement, which may be covered by your car's warranty or your auto-insurance policy.

The most reliable way to order a new key fob is through your vehicle's dealership or an authorized service center. They can provide you with the correct part number and order it directly from the manufacturer.

Still have questions? Speak to one of our Tinker Experts today!

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