The battery in your Prius key fob dies like any other battery, and you can replace it yourself without tools or a trip to the dealer
Your Prius key fob uses a small coin-cell battery—usually a CR2032—that lasts three to four years depending on how often you use the remote lock and unlock buttons. When the fob stops working or the buttons become sluggish, the battery is almost always the culprit. You can buy a replacement battery at any drugstore, grocery store, or hardware store for $3 to $8, and the swap takes about two minutes once you have the battery in hand.
The process is the same whether you drive a first-generation Prius (2004–2009), second-generation (2010–2015), third-generation (2016–2023), or the newer models. No special tools, no dealer visit, and no programming required afterward.
Key Takeaways
- Prius key fobs use a CR2032 coin-cell battery that you can buy at any pharmacy or grocery store for a few dollars.
- The fob opens by sliding a small metal tab or pressing a release button on the back—no screwdriver needed.
- Remove the old battery, note which side faces up, and insert the new one the same way.
- Test the buttons before closing the fob; if they still do not work, the battery may be installed backwards or the fob may have a different problem.
- If the fob still does not work after a fresh battery, the circuit board inside may be damaged and the fob will need replacement.
What battery your Prius key fob uses
Nearly all Prius key fobs use a CR2032 battery, a flat, round coin-cell battery about the size of a dime. A few older or aftermarket fobs may use a CR2025 or CR2016, but CR2032 is the standard. When you buy a replacement, the package will say "CR2032" clearly on the front.
You do not need a special automotive battery. A CR2032 from a pharmacy, grocery store, dollar store, or hardware store works exactly the same as one sold at a car dealership, and it costs a fraction of the price. Buy one or two extras while you are there—they last years in storage and are handy to keep around.
How to open your Prius key fob
Look at the back of your fob. You will see either a small metal slot or a raised button or tab. This is the release mechanism.
If your fob has a metal slot: Insert a coin (a penny or dime works) into the slot and turn it gently counterclockwise, as if you were opening a battery compartment on a flashlight. The two halves of the fob will separate. Do not force it—a quarter turn is usually enough.
If your fob has a button or tab: Press or slide it in the direction the arrow points (if there is one marked). The fob will pop open or the back cover will slide off. Again, gentle pressure is all you need.
Once the fob is open, you will see the battery sitting in a small metal holder. It is a flat, shiny disc, usually silver or gold in color.
Removing and replacing the battery
Look at which side of the battery is facing up—this matters. The battery has a positive side (marked with a + symbol) and a negative side. Most CR2032 batteries have the + side facing up when installed correctly in a Prius fob.
Gently pry the old battery out using your fingernail or the edge of a coin. It should come free with light pressure. If it is stuck, do not dig at it with a sharp object—you risk damaging the metal contacts inside the fob.
Drop the new CR2032 battery into the holder with the same side facing up as the old one was. If the + symbol is visible on top, the + side is facing up. Press down gently until you hear or feel a small click—the battery is now seated.
Close the fob by reversing how you opened it: turn the coin counterclockwise if you used a slot, or slide the cover back on if it slides. The two halves should fit snugly with no gaps.
Testing your fob after battery replacement
Stand a few feet from your Prius and press the lock button. You should hear the car lock and see the lights flash. Press unlock and listen for the unlock sound. If both buttons work and the response is quick, the battery is installed correctly and you are done.
If the buttons do not work or respond slowly, open the fob again and check that the battery is sitting flat in its holder and facing the right direction. A battery installed backwards will not work at all. Flip it over, close the fob, and test again.
If the fob still does not work after you have tried a fresh battery installed both ways, the problem is likely inside the fob itself—a damaged circuit board or corroded contacts. At that point, the fob needs to be replaced rather than repaired. You can order a replacement fob online or buy one from a Toyota dealer, though dealer fobs are more expensive.
When to replace the whole fob instead of just the battery
Most of the time, a dead fob is just a dead battery. But if you have installed a fresh CR2032 and tested it both ways and the buttons still do not work, the fob has an internal problem. Water damage, a cracked circuit board, or corroded battery contacts can all prevent the fob from working even with a good battery.
Replacement fobs are available online through retailers like Amazon or eBay, typically in the $15 to $40 range depending on the model year. Toyota dealerships also sell fobs, usually for $50 to $150 plus programming. If you buy a fob online, check the listing carefully to make sure it matches your Prius model year—a 2015 fob will not work with a 2020 Prius, for example.
Most aftermarket fobs come pre-programmed and work as soon as you install the battery. If a fob does not work after battery installation, the listing should say whether it needs programming at a dealership. Some do, some do not.
Keeping your key fob battery healthy
Key fob batteries last longest when you avoid unnecessary button presses and keep the fob away from heat and moisture. Leaving your fob in a hot car, dropping it in water, or sitting on it can all shorten battery life or damage the fob itself.
If you have a spare fob, rotate between them—using one fob heavily while the other sits in a drawer means neither battery drains as fast. When you replace the battery in one fob, check the spare at the same time. If the spare is working fine, its battery is still good, but if it is sluggish, replace that battery too.
Store spare fobs in a cool, dry place away from direct sunlight. A desk drawer or junk drawer in your house is ideal. Avoid leaving fobs in the car, where heat can damage the battery and the circuit board.
Frequently Asked Questions
Can I use a different battery size if I cannot find a CR2032?
No. A CR2025 or CR2016 will not fit properly in the holder, and a battery that is too large can damage the contacts. Stick with CR2032. If your local store is out of stock, order one online—they ship fast and cost just a few dollars.
Do I need to reprogram my Prius after changing the key fob battery?
No. Changing the battery does not erase any programming. Your fob will work exactly as it did before, as soon as the new battery is installed and the fob is closed.
What if one button works but the other does not?
A single button failing usually means the battery is installed backwards or not seated all the way. Open the fob, check the battery position, and make sure it is sitting flat in the holder. If both buttons still do not work after you have checked the battery, the circuit board inside the fob may be damaged.
How long does a CR2032 battery last in a Prius key fob?
Most CR2032 batteries last three to four years in a Prius fob, depending on how often you use the remote lock and unlock buttons. Heavy use can shorten that to two years; light use can stretch it to five years or more.
Can I buy a Prius key fob battery at a Toyota dealership?
Yes, but you will pay more than at a pharmacy or hardware store. Dealerships typically charge $8 to $15 for a CR2032 battery, while the same battery costs $3 to $5 elsewhere. The battery itself is identical no matter where you buy it.