On many Mazdas, the green KEY light on the dash flashes for about 30 seconds after you shut the engine off. Some models show a “Low Key Fob Battery” message in the display instead. Or you press a button on the fob and the doors don’t respond. All of these point to the battery in your key fob.
A Mazda key fob battery is a coin cell you can replace yourself. Older keys use a CR2025 and newer keys use a CR2032, so match the battery you take out. Put the new battery in positive side up. If you’d rather not open the fob, we can do it for you.
How do I know if my Mazda key fob battery is low?
A flashing green KEY light after you shut off the engine, a low battery message in the display, or fob buttons that do nothing usually mean the battery is running down. What you see depends on your model.
| What you notice | What it can suggest | Best next step |
|---|---|---|
| The green KEY light flashes on the dash for about 30 seconds after you shut the engine off, or a low battery message appears in the display. | The fob battery is getting low, but the fob still works. | Replace the battery soon, before the fob stops working. |
| You press the fob buttons, nothing happens, and the light on the fob doesn’t flash. | The battery may be dead. | Replace the battery. You can still get in and start the car in the meantime. |
| The fob buttons still lock and unlock the car, but the doors won’t unlock when you touch the handle, the engine won’t start with the fob in your pocket, and the light on the fob never flashes. | The fob’s power saving mode may be turned on. | Turn power saving mode off before you buy a battery. |
| The green light on the start button flashes when you try to start the car. | The car can’t read the fob, which can mean the fob battery is dead. | Touch the fob to the start button to start the engine, then replace the battery. |
| The amber light on the start button flashes. | A malfunction in the push button start system. | Schedule service so we can look at it. |
Could my Mazda key fob be in power saving mode instead of needing a new battery?
Yes. Many newer Mazdas have a power saving mode for the fob that can be switched on by accident, and it can make a fob with a good battery seem dead.
Power saving mode turns off the hands-free features: unlocking the doors by touching the handle, and starting the car with the fob in your pocket. The buttons on the fob still lock and unlock the car, but the small light on the fob stops flashing.
To turn it off, press any button and confirm the light on the fob doesn’t flash. Then press the lock button four times within three seconds, which turns the light on. Hold the lock button for at least 1.5 seconds while the light is on. The hazard lights flash once to confirm. The exact steps can differ a little by model, so if it doesn’t work, bring the fob in and we can take a look.
Which battery does my Mazda key fob use, a CR2025 or a CR2032?
It depends on the key. Older keys, like the ones on 2016 to 2018 CX-5, CX-9, Mazda3, and CX-3 models, use a CR2025. Newer keys, which started with the 2019 Mazda3 and reached most of the lineup in 2020, use a CR2032, and so does the 2024 CX-90.
Some models, like the 2020 CX-5, were built with either style of key, so don’t go by the model year alone. Look at the battery you take out and buy the same type. The wrong one can keep the fob from working properly.
How do I replace a Mazda key fob battery?
You need a flathead screwdriver, some tape, and the new battery. On models from 2016 on, Mazda keys open one of two ways, and the steps differ.
If the metal key pulls straight out of the fob:
- Press the release knob and pull the metal key out.
- Wrap the tip of the screwdriver in tape. Twist it into the seam to open the cover slightly, slide it along the gap, then twist again to lift the cover off.
- Take off the small battery cap, then lift out the old battery. If there’s a rubber ring around the battery, keep it from getting scratched. If it comes loose, put it back before the new battery goes in.
If the lower cover of the fob slides off:
- Slide the release knob and take the lower cover off.
- Press in the tab to release the upper cover.
- Slide the taped screwdriver into the gap, then twist it to lift the upper cover off.
- Pry the battery cap off with the screwdriver, then lift out the old battery.
Put the new battery in with the positive side facing up. Then reassemble in the opposite order: the cap, then the cover, then the metal key. On the slide-off style, the upper cover goes on first, and then the lower cover with its tabs fitted into the slots.
Keep your fingers off the circuit board and the metal contacts, don’t bend the contacts, and keep dirt out of the fob. A battery that goes in the wrong way around can leak. When you’re done, press a button. The light on the fob should flash and the doors should respond.
If you can’t tell which style you have, your key doesn’t open the way these steps describe, or you’d rather not pry it open, bring it to us. Replacing the battery incorrectly can damage the key.
How do I start my Mazda when the key fob battery is dead?
Use the metal key to unlock the door, then start the car by touching the fob to the start button.
Put your foot on the brake pedal, or the clutch if your Mazda is a manual. Wait for the green light on the start button to flash. Touch the start button with the back of the fob, with the buttons facing up and the emblem lined up with the center of the button. When the green light stays on, press the button to start the engine.
Keep other keys, metal objects, and payment or building access cards away from the fob while you do this, or the car may not pick up its signal. Starting the car this way doesn’t fix the fob, so replace the battery as soon as you can.
What drains a Mazda key fob battery or damages the fob?
A fob that picks up high-intensity radio waves can use up its battery faster, so don’t leave it sitting next to a TV. Water damages a fob, and so do drops, heavy objects, and magnets.
If you drive onto the sand at one of the beach ramps off A1A and head for the water, take the fob out of your pocket first and keep it dry.
What happens when I bring my Mazda key fob to Daytona Mazda Service Center?
Bring the fob in and we can take care of the battery for you. Part of that is making sure the replacement is the right type for your key, since the wrong one can keep the fob from working properly. If the fob still doesn’t respond after a new battery, we can look into the fob itself and the keyless system in the car.
You can schedule service at Daytona Mazda Service Center when you’re ready.
Mazda Key Fob Battery Questions in Daytona Beach, FL