Short answer
If your key fob stops working, its coin battery is usually dead. Slide out the hidden metal key to open the driver’s door. In a push-button car, hold the fob right against the start button and push the button with it. Then replace the fob battery: open the case at its slot, match the number on the old battery and put the new one in the same way.
Safety first
Keep coin batteries, new and used, away from children and pets. A swallowed coin battery can cause serious burns inside the body in hours: if you think a child swallowed one, call 911 right away.
What to do when your key fob stops working
1You press the button and nothing happens
The car does not respond. If it works only up close, the fob battery is weak. If the car also seems dead, check the car battery.
Read all the steps
- You press the button and nothing happens. The car does not respond. If it works only up close, the fob battery is weak. If the car also seems dead, check the car battery.
- Use the hidden key in the fob. Press the small release and slide out the metal key. Use it in the driver’s door lock. Some locks hide under a little cap on the handle.
- Push-button start? Fob against the button. The car can read a fob with a dead battery from very close. Hold it on the start button, press the brake and push the button with the fob.
- Swap the coin battery, plus side up. Open the case at its slot with a coin or a small flat screwdriver. Match the number on the old battery, like CR2032, and put the new one in the same way.
- Test it: the car answers again. Press each button. The lights should flash. If it still does not work, the fob may need to be reprogrammed.
- Still not fixed? Call a mechanic Especially if: a new fob battery did not fix it.
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Fob battery or car battery?
- Fob works only up close: the fob battery is weak.
- Fob works, but the car will not start and the dash is dim or dark: the car battery is weak.
- The spare fob works but this one does not: this fob is the problem.
- Neither fob works: the car battery, a fuse or the car’s receiver.
What not to do
- Do not pry the case open with a knife: it slips and cuts.
- Do not touch the flat faces of the new battery with oily fingers. Hold it by the edges.
- Do not leave spare coin batteries where kids or pets can reach them.
When to call a mechanic
- A new fob battery did not fix it.
- The fob is cracked, got wet or the buttons are worn out.
- You lost your only fob or need a spare programmed.
- Neither fob works and the car battery is fine.
Frequently asked questions
How do I know if my key fob battery is dead?
The range gets shorter, you have to press the buttons several times, or a "key not detected" message appears. Fob batteries usually last a few years.
What battery does a key fob take?
Most use a flat coin battery, often a CR2032 or CR2025. The number is printed on the old battery, so check it before you buy.
Can I start my car if the key fob is dead?
Usually yes. Hold the fob right against the start button, or in the fob slot some cars have, and push the button with it. Your owner’s manual shows the exact spot.
Do I need to reprogram my key fob after changing the battery?
Most fobs keep working after a battery swap. Some need a simple reset in the car, explained in the manual. If it still does not work, a dealer or an automotive locksmith can reprogram it.
Where is the hidden key in my fob?
Look for a small button or slider on the side or back of the fob. Press it and pull the metal key out.
Is it the car battery or the key fob?
If the dash lights and headlights are bright, the car battery is fine and the fob is the likely problem. If everything is dim or dark, start with the car battery.