Car Key Fob Battery Replacement: Which Battery and How to Change It
Key fob battery replacement is one of the cheapest, easiest car fixes you can do. Most car key fobs use a small 3-volt lithium coin battery, most often a CR2032, sometimes a CR2025, CR2016 or CR1632. To replace it, pry the fob open at its seam, note which way the old battery faces, swap in the same type with the positive (+) side the same way, and snap the fob closed. It takes about five minutes, costs $5 to $15, and in most cars the fob does not need reprogramming afterward.
This guide shows how to find the right battery, change it step by step, start your car if the fob is dead, and what to do if the fob still will not work.
Key Takeaways
- Most common battery: CR2032; check the old battery or your owner’s manual.
- Signs it is low: shorter range, pressing buttons several times, or a “key battery low” message.
- Reprogramming: usually not needed after a battery change.
- Dead fob? Hold it against the start button or use the hidden mechanical key.
- Keep coin batteries away from children: swallowing one can cause serious injury.
Signs Your Key Fob Battery Is Low
- You have to stand closer to the car for the buttons to work
- Buttons need several presses
- The keyless entry or push-button start works only sometimes
- A “Key battery low” or “Key not detected” message on the dashboard
- The small LED on the fob is dim or does not light
Key fob batteries typically last about two to four years, depending on use and whether the car has keyless entry, which keeps the fob communicating more often.
Which Battery Does My Key Fob Use?
| Battery | Thickness | Common use |
|---|---|---|
| CR2032 | 3.2 mm | The most common key fob battery |
| CR2025 | 2.5 mm | Thinner fobs |
| CR2016 | 1.6 mm | Very thin fobs; sometimes two stacked |
| CR1632 | 3.2 mm (16 mm wide) | Some Toyota, Lexus and other fobs |
| CR1620 / CR1220 | Various | Some older or smaller remotes |
The easiest way to know is to open the fob and read the code printed on the old battery. Your owner’s manual also lists it. CR2032, CR2025 and CR2016 share the same 20 mm diameter but differ in thickness, so a thinner battery may fit but can lose contact. Use the exact type your fob calls for.
How to Replace a Key Fob Battery
- Release the mechanical key if your fob has one; there is usually a small button or slide.
- Find the seam or notch where the two halves of the fob meet. Some fobs have a slot for a coin or small flat screwdriver; a few have a tiny screw.
- Gently pry the fob open, working around the edge. Wrap the screwdriver tip in tape or a cloth to avoid scratching the plastic.
- Note the battery orientation, usually positive (+) side up, before removing it. Taking a quick photo helps.
- Remove the old battery with a plastic tool or fingernail, avoiding touching the circuit board.
- Insert the new battery the same way, holding it by the edges.
- Snap the fob back together and reinsert the mechanical key.
- Test it: lock and unlock the car and start it.
Safety note: coin and button batteries can cause severe internal burns within hours if swallowed. Keep new and used batteries out of reach of children and pets, and seek emergency medical help immediately if one may have been swallowed.
How to Start Your Car When the Key Fob Is Dead
- Push-button start cars: hold the fob right against the start button, or place it in a designated backup spot such as a slot in the console or cup holder, then press the start button with your foot on the brake. The car can read the fob’s chip even when the battery is dead. Check your owner’s manual for the exact location.
- Getting in: use the mechanical key hidden inside the fob. Some cars hide the door keyhole under a small cap on the handle.
- Traditional key fobs with a key blade still start the car normally; only the remote buttons stop working.
Does the Key Fob Need Reprogramming After a Battery Change?
Usually no. The code that pairs the fob to your car is stored in memory that does not need battery power. A few models may need a quick resync, often by pressing lock and unlock or starting the car with the fob, if the fob was left without a battery for a long time. If the fob still will not work after a battery change, check the battery type and orientation, clean the contacts, and see your owner’s manual or a dealer or locksmith. If your fob or keyless system acts up after a battery swap, check the NHTSA recall lookup for software recalls.
What Does Key Fob Battery Replacement Cost?
| Option | Typical cost |
|---|---|
| DIY battery (single or multi-pack) | $5–$15 |
| Auto parts or battery store | Battery price; some stores install it for free |
| Dealer or locksmith | About $15–$60, including the battery |
| New key fob if the fob itself fails | $100–$700+ depending on type |
If the Fob Still Does Not Work
- Make sure the battery is the correct type and fully seated, with the right side up.
- Try a battery from a different pack; some cheap batteries arrive weak.
- Clean the battery contacts gently with a cotton swab and a little rubbing alcohol.
- Try the spare fob. If the spare works, the problem is the fob; if neither works, the car’s receiver or a car battery problem may be at fault.
- Check the car battery; a weak car battery can stop keyless entry from working.
- Ask a locksmith or dealer to test and, if needed, reprogram or replace the fob.
Tips to Make Fob Batteries Last Longer
- Keep the fob away from your phone and other electronics when not in use.
- Do not store the fob right next to the car at home; some keyless systems keep communicating with it.
- Replace both fobs’ batteries at the same time so you have a reliable spare.
- Keep a spare battery in the glove box.
Key Fob Battery FAQ
Most use a 3-volt lithium coin cell, most commonly a CR2032, though some use a CR2025, CR2016 or CR1632. Check the old battery or your owner manual.
Only as a short-term emergency fix. They have the same diameter, but a CR2025 is thinner and may lose contact and run down faster.
Pry the fob open at the seam, note the battery orientation, replace it with the same type facing the same way, snap the fob closed and test it.
Usually not. The pairing code is stored in memory that does not need battery power. A few models may need a quick resync.
Typically about two to four years, depending on use and whether your car has keyless entry.
For push-button start, hold the fob against the start button or place it in the backup slot shown in your manual, then press start with your foot on the brake.
About $5 to $15 to do it yourself, or roughly $15 to $60 at a dealer or locksmith.
The battery may be the wrong type, upside down or weak, the contacts may be dirty, or the fob may need resyncing or repair.
