Key Fob Not Working? Dead Battery or a Bad Fob

A fob usually gives some warning before it quits: you press the button twice, you walk closer, the car hesitates. Then one day nothing happens at all. Before you assume the fob is broken, it helps to know what a dying battery looks like, what a failed fob looks like, and what you can safely try yourself.

Signs the battery is running down

• You have to be closer to the car than you used to.
• It takes two or three presses before the car reacts.
• The dashboard shows a message like “key battery low” or “key not detected”.
• It works some days and not others, often worse in cold weather.
• The small light on the fob, if it has one, is dim or doesn't flash.

A fob battery lasts a few years in normal use. If yours is still on its original battery and the car is a few years old, that's the first suspect.

How to change a fob battery

On most fobs this is a small job you can do at the kitchen table. Check your owner's manual first, because the way the case opens varies from car to car.

1. Look for a small button or slide that releases the metal backup key, and take the key out. On many fobs the gap it leaves is where the case opens.
2. Open the case gently at that notch with a coin. Work slowly around the edge rather than forcing one spot.
3. Note which way up the old battery sits before you take it out.
4. Read the code printed on it, a short one like CR2032, and fit a new one of exactly that type, the same way up.
5. Close the case until it clicks all the way around, put the key back and test the buttons.

Still not working with a new battery?

Then narrow it down before you replace anything:

• Try the spare fob. If the spare works, the problem is the first fob. If neither works, look at the car instead.
• Check the car's own battery. A weak car battery can stop the car from answering any fob, and it usually shows in other ways too: slow cranking, dim lights, warning messages.
• Look for damage. A fob that has been dropped, sat on or put through the wash can crack inside or corrode. Rattling, or a button that no longer clicks, are bad signs.
• Check the manual for a resync step. Some cars need the fob paired again after a battery change, and the manual shows how when the owner can do it.

If the spare works and the first fob still doesn't, even with a fresh battery, it's time for a replacement.

The hidden key inside the fob

Almost every modern fob hides a small metal key for the day the battery dies. It opens the driver's door by hand. On some cars the keyhole is out of sight, under a small cap on the driver's door handle, and your owner's manual shows how that cap comes off.

Once you're inside, the car usually still has a way to recognize a fob with a dead battery. The manual shows the exact spot to hold the fob so the car can read it, and it's worth looking that up now, before you need it.

When the fob has to be replaced

A fob that's lost, broken, or no longer recognized even with a new battery needs replacing, and a new fob has to be programmed to the car before it does anything. That's part of our car key replacement work, done at the vehicle.

When you call, have the year, make and model ready, tell us whether you still have a working key, and say whether the car has a push-button start. If you have no working key at all, our guide on losing the only car key explains how that changes things.

Looking after a fob

• Change the battery every few years, before it fails, not after.
• Keep the fob away from water and out of the laundry.
• Don't keep it on a heavy key ring. The weight wears the case and the buttons.
• Keep the spare fob somewhere safe, and check once in a while that it still works. Its battery runs down too, even in a drawer.