How to Replace a Key Fob Battery

Quick answer: most key fob batteries are flat, coin style cells, usually a CR2032 or CR2025, that you can replace yourself in about two minutes. You open the fob at the seam, swap the old cell for a fresh one with the same number, snap it shut, and test the buttons. If the fob still will not respond after a new battery, the problem is something else, and we cover that below.
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Signs your key fob battery is dying

A fading battery rarely quits all at once. You usually get warning signs first. You might notice you have to stand closer to your car for the doors to respond, or that you are pressing the button two or three times instead of once. Some vehicles flash a low key battery message on the dash. On push to start cars, the engine may be slow to recognize the fob, or you may need to hold the fob right against the start button to get it going.

Here on Oahu, we see batteries fade a little faster than the mainland average. Heat and humidity are hard on small electronics, and if you park near the water in spots like Waikiki or Hawaii Kai, salt in the air does not help either. A fob that bakes in a hot car all day in a Kapolei parking lot works harder than one kept in a cool garage.

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Find out which battery your fob uses

Before you buy anything, check what your fob actually takes. The number is printed right on the old battery once you open the fob, so the safest move is to open it first and read the cell. Most fobs use a standard coin cell battery, with the CR2032, CR2025, and CR1632 being the most common. They look similar but differ in thickness, so matching the exact number matters.

Different makes use different cells, so a Toyota fob may not take the same battery as a Subaru or a Nissan. If you would rather know before you open it, your owner's manual lists the battery type, and most auto parts shops on the island can match it if you bring the fob in.
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How to replace a key fob battery, step by step

1. Look for the seam or a small notch along the edge of the fob. Many fobs also hide a metal emergency key inside that you slide out first to reveal the opening.
2. Gently pry the two halves apart at the seam using a small flat tool. A coin or a plastic pry tool works better than a screwdriver, which can scratch or crack the case.
3. Note how the old battery sits, which side faces up, before you remove it. Take a quick photo with your phone if you want a reference.
4. Pop out the old cell and drop in the new one the same way up. The writing on the battery usually faces the back cover.
5. Snap the halves back together until you hear a click, slide the emergency key back in if you removed it, and test every button.

If everything lights up and responds, you are done.
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When a new battery does not fix it

A fresh battery solves the problem most of the time, but not always. If your fob still will not work, a few other things could be going on. The fob may have lost its programming and need to be re-synced to your vehicle, which can happen after the battery has been dead for a while. The buttons or internal board may be worn out, especially on an older fob that has taken years of daily use and island humidity. In some cases the fob is fine and the issue is on the car's side.

If you have ruled out the battery and the convenience features still will not work, that is where we come in. Our team can replace your key fob battery, re-sync a fob, or set you up with a replacement fob for nearly every make on the road in Honolulu. If you want to understand how these remotes work in the first place, our guide on what a key fob is breaks it down.
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Frequently asked questions

How long does a key fob battery last?

Most last three to four years, though heavy daily use and the island climate can shorten that.

Will replacing the battery erase my fob's programming?

On the vast majority of vehicles, no. The programming is stored in the fob and the car, not the battery. A small number of models may need a quick re-sync, which is a simple fix.

Can I drive if my key fob battery dies completely?

Usually yes. Most push to start vehicles let you start the car by holding the dead fob against a specific spot, often the start button or steering column. Your owner's manual shows the exact method for your model.

Should I replace the battery or the whole fob?

If the fob is physically intact and only the battery is weak, a new battery is all you need. If the case is cracked or the buttons are failing, replacement is the better long term call.
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Need a hand on Oahu?

Stuck with a fob that will not cooperate? Honolulu Locksmith can sort it out fast, whether it is a battery, a re-sync, or a full replacement. Learn more about our key fob battery replacement and full range of auto locksmith services.

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