How Do You Start Your Car When Your Key Fob Battery Dies?

Your ignition will still work even if your key fob battery won't.

Benjamin Hunting | 

Mar 17, 2023 | 3 min read

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Once you own a car that uses a key fob, it may be hard to imagine life without one. Modern fobs offer keyless entry, remote starting, and even the ability to open doors, hatches, and trunks without fumbling for a key. Many vehicles also allow you to leave the fob in your pocket and fire up the ignition with the push of a button.

So, what happens when your trusty key fob's battery dies and you need to start your car? Here's how you can unlock your ignition and get your motor running even with a dead fob.

How Do Key Fobs Work?

Key fobs are miniature, battery-powered radio transmitters that broadcast a signal to a receiver in your vehicle. Although the transmission is only powerful enough to travel a modest distance, the signal is encoded to make it difficult for anyone to intercept it. The fob sends commands to a vehicle's onboard receiver, which then tells its computer controller to either unlock the doors, open the rear hatch, or start the ignition.

The starter button relies on a specific signal from the fob that lets the vehicle know the fob is in close proximity to the driver's seat. The presence of the fob is what allows you to start the engine when you push the button.

What If My Key Fob Battery Dies?

A dead battery in your key fob means it can’t broadcast the signal the ignition system is looking for. If your car or truck can't detect the correct signal, then the ignition will remain locked, and you won't be able to start your car with the fob in your pocket.

Fortunately, your car has a backup system that accounts for this problem. For most brands, if you hold your dead fob up against the ignition button, the close proximity will allow the vehicle to verify the presence of the key and start the car.

Some vehicles have a slot on the dash, the center console, or the steering column where you can insert the fob (or hold it against it), to get it as close to the receiver as possible. Your owner's manual should tell you where to look.

If that doesn't work, a small number of automakers combine the fob with a physical key or conceal a small key inside the fob itself. This key is sometimes used in a hidden slot on the steering column that will function like a traditional ignition.

Remote Start to the Rescue

Finally, you could try calling the manufacturer's remote services department to have them start your car using its data connection. Many car companies offer an app with this type of remote ignition start functionality. Some apps even take the form of a digital “key” that can replace the fob if necessary.

Benjamin Hunting

Benjamin Hunting is a writer and podcast host who contributes to a number of newspapers, automotive magazines, and online publications. More than a decade into his career, he enjoys keeping the shiny side up during track days and always has one too many classic vehicle projects partially disassembled in his garage at any given time. Remember, if it's not leaking, it's probably empty.