Your car, which once sprang to life with a simple button, now gives you the silent treatment. After a few frantic presses, the door finally unlocks, and you see the “Key Fob Battery Low” alert flashing on your dashboard.
No need to panic. The fix is simple — a quick and careful battery swap.
Not sure where to start?
In this article, we’ll cover everything you need to know when your key fob battery is low — from spotting the signs to replacing it. We will also share tips on how to select a new key fob battery.
This Article Contains:
- What Does the “Key Fob Battery Low” Warning Mean?
- 5 Key Signs that Indicate Your Key Fob Battery is Low
- What to Do When Your Key Fob Battery is Dead
- How to Identify the Right Battery for Your Car Key
- How to Replace a Key Fob Battery
- 3 FAQs About Key Fobs
What Does the “Key Fob Battery Low” Warning Mean?
The “Key Fob Battery Low” warning message means that the battery inside your car’s key fob is running out of power.
The key fob relies on a small internal battery to function — just like your car battery that powers the engine and electronic devices. When the battery is low, the fob may stop working properly.
Now that you know what the low battery warning sign means, let’s explore the symptoms that come with it.
5 Key Signs that Indicate Your Key Fob Battery Is Low
You might be dealing with a depleted key fob battery if you notice:
- Weakened signal strength: If the remote start key only works when you’re very close to your vehicle, it’s likely due to a weakening battery.
- Unresponsive buttons: An unlock button that requires multiple presses or extra pressure to work may indicate a low battery.
- Engine fails to start with push button: In push-button start vehicles, the key fob communicates with the car’s computer to enable engine ignition. If the fob’s battery is low, it may fail to transmit this signal correctly. Consequently, the engine might not start when you press the ignition button. Additionally, you may see a warning message like “Key Not Detected” on the dashboard.
- Dim or non-functioning LED light: Most key fobs have a small LED that lights up when you press a button. A dim or non-functioning light is another symptom that accompanies a low battery warning sign.
- Dashboard warning light: Some vehicles display a dashboard warning light when the key fob battery is low, allowing you to replace it before it dies completely.
Have you noticed one or more of these symptoms recently?
Here’s how to deal with it.
What to Do When Your Key Fob Battery is Dead
Try these steps if you have a dying or dead fob battery:
1. Move Closer to the Car
If the key fob battery isn’t completely drained, standing closer to the vehicle may help it connect and unlock the doors.
2. Use the Mechanical Key
Most remote start keys come with a hidden mechanical key inside, designed for situations when keyless entry fails.
Here’s how to use this spare key:
- Look for a release button or latch on the fob — press and hold it to slide the metal key out. You can then use the spare key to manually unlock the driver’s side door.
- To access the keyhole, use the physical key to remove the cover on the door handle.
- In vehicles with a flush door handle, press the front part of the handle to reveal the keyhole at the rear. Once the keyhole is exposed, insert the physical key and turn it to unlock the door.
3. Try Remote Unlocking
If your car is connected to a mobile app or online service, you may be able to unlock it using your phone or customer support. If you’re unsure, contact your dealership service center for assistance.
4. Start the Car
If you’re able to unlock the car — whether using the mechanical key or a connected app — the next step is to try starting it. For vehicles with push-button start, the system might still detect a weak key fob battery through low-frequency signals. Place the key fob directly next to the start button and press it.
Some vehicles also have a slot near the center console to insert the fob and start the engine even with a dead battery.
5. Call for Professional Help
If none of the above methods work, you may need to contact a mobile mechanic or roadside assistance service. They can come to your location to replace the dead battery and unlock the car.
Before replacing the battery, make sure to purchase one that fits your key fob exactly.
Keep reading to figure out which one you need.
How to Identify the Right Battery for Your Car Key
Use these handy tips to find the perfect match:
- Identify your key type: Different car keys, such as standard remotes or smart keys, use different batteries. Refer to your vehicle’s user manual or contact the manufacturer to determine your key and battery type.
- Check the old battery: Open the fob and check the existing battery. Most batteries will have their type and model number printed on the surface. Use this information to ensure an exact match when purchasing a fresh battery.
- Confirm the battery size: Key fob batteries come in standardized sizes, often indicated by a combination of letters and numbers (e.g., CR2032 battery). To prevent compatibility issues, refer to your vehicle’s user manual to identify the correct replacement battery size.
- Match the voltage and type: Car key fobs typically use a 3-volt lithium coin-cell battery, commonly known as a button battery. Always confirm the voltage to ensure your replacement battery delivers the same power as the original.
- Choose a reliable brand: Opt for reputable battery brands known for their durability. A high-quality fresh battery lasts longer and reduces the risk of malfunction.
NOTE: It’s smart to keep a spare battery for your key fob. But don’t store the spare battery in the car, as it won’t do you any good if you’re locked out.
After identifying the correct battery type, you can choose whether to replace it yourself or seek professional help.
How to Replace a Key Fob Battery
You can replace a key battery yourself if you’re familiar with the process. However, be careful while opening the fob, as the small plastic tabs that hold it together can break easily. Also, ensure you install the new battery in the same direction as the old one, or the fob won’t work.
If you’re unsure at any point, it’s best to contact a technician.
Here’s how you can proceed with the battery replacement:
- Locate the latch, switch, or screw at the back of the car key fob and open it using fingernails or a small flathead screwdriver. Pull apart the two halves once the fob’s battery cover is open.
- Remove the old battery. If the key battery fob has clips over the battery — use a screwdriver to lift them carefully without damaging the circuit board.
- Place the new battery inside the fob and close up the fob.
- Test to see if the keyless entry system works fine. If the fob unlock button isn’t working, reset the programming instructions in the following manner:
- Insert the ignition key and turn it to the ‘On’ position without starting the engine. This activates the vehicle’s electrical system and gets it ready for programming.
- Press and hold the lock button on the key fob for about five seconds. This signals the vehicle’s electronic control unit that the programming process is starting.
- Turn the key back to the ‘Off’ position. Depending on the vehicle model, repeat the on-off cycle several times, as specified in the owner’s manual.
- Test the key fob by using it to lock and unlock the doors to ensure it’s working properly.
NOTE: Some vehicles come with a second fob, giving you a backup to open and start your car in case the first one gets lost. You should store the second fob in a Faraday pouch, as this blocks all wireless signals and prevents accidental activation.
Still got questions?
The next section covers additional facts about a car key fob to help clarify your doubts.
3 FAQs About Key Fobs
Here are the answers to some commonly asked questions about key fobs:
1. How Much Does Replacing Key Fob Batteries Cost?
A new key fob battery, typically a coin-type (such as a CR2032 battery), costs between $2 and $10, depending on the brand.
If you prefer a service center or an auto repair shop, the total cost can range from $20 to $50, including both the battery and labor.
2. How Long Do Key Fob Batteries Last?
The battery life depends on whether you’ve got a regular remote key fob or a smart key.
A regular fob battery can last for four to six years, while the battery life for a smart key is around two to three years.
3. What’s the Difference Between a Smart Key and a Regular Key Fob?
A regular remote key fob lets you control basic functions like locking and unlocking the doors, opening the trunk, or triggering a panic alarm. These functions are activated by pressing buttons on the fob.
A smart key, on the other hand, offers a more advanced and hands-free keyless entry system. It uses wireless communication (such as radio frequency or Bluetooth) to interact with your smart vehicle. Even while the smart key stays in your pocket, the car unlocks when you touch the door handle and starts when you push the ignition button.
Choose AutoNation Mobile Service for a Reliable Key Fob Battery Replacement
That tiny button battery might seem insignificant, but it enables your car to start without a hassle. If it’s getting sluggish, don’t ignore it — replace the old cell before it locks you out on the worst possible day.
If you aren’t sure how to do it yourself or if you’re dealing with any other car issues, you can always reach out to the experts at AutoNation Mobile Service.
We are available seven days a week with upfront pricing on all kinds of car repairs. We even back them with a 12-month and 12,000-mile warranty for your peace of mind.
Contact us for reliable car care.