Replace the Key Fob Battery

Last updated: June 12, 2026

If the remote on your Mazda 2 Mk3 (DJ/DL, 2015–2022) has become weak — you have to stand close to lock or unlock, or a “key battery low” message has appeared — the fob’s coin cell needs replacing. Depending on trim the Mazda 2 came with a keyless smart key (CR2025) or a standard remote (CR2032). This guide covers both, including the easy-to-miss O-ring on the smart key.

Which Key Do You Have?

• Type 1 — keyless smart key: push-button start cars; has a pull-out emergency blade. Takes a CR2025 and has a rubber O-ring seal.
• Type 2 — standard remote: a fob with a separate battery cover. Takes a CR2032.

Type 1 — Smart Key (CR2025)

1. Push and hold the release knob and pull the metal emergency key out of the fob.
2. Insert a screwdriver (tape sharp edges) into the slot and gently separate the two halves of the case.
3. Pull out the button-cell cover and lift out the old CR2025 cell.
4. Fit the new cell with the positive (+) side facing up.
5. Check the rubber O-ring is not distorted or displaced — it keeps moisture out, so seat it correctly.
6. Click the cases together and slide the emergency key back in.

Type 2 — Standard Remote (CR2032)

1. Remove the key cover — press the retaining tab and use a flat-bladed screwdriver to release it.
2. Remove the battery cover and lift out the old CR2032 cell.
3. Fit the new cell with the positive (+) side facing up.
4. Refit the battery cover and the key cover.

Test It

Lock and unlock the car from a normal distance. If keyless start reads the fob reliably and the low-battery message has gone, you are done. A new cell typically lasts a couple of years.

Does It Need Programming?

No — replacing the coin cell does not affect the fob’s pairing, so the key keeps working immediately. Programming a brand-new or replacement key requires Mazda’s diagnostic tool (M-MDS) at a dealer or auto locksmith.

Frequently Asked Questions

What battery does the Mazda 2 Mk3 key take?

The keyless smart key uses a CR2025; the standard remote uses a CR2032. Check which style you have before buying.

Will the car still start if the smart-key battery dies?

Yes. Hold the fob against the start button (Mazda marks the spot) to start using the backup transponder. The emergency blade in the fob unlocks the door.

Why does the O-ring matter on the smart key?

It seals the fob against moisture. If it’s pinched or left out, damp can get in and corrode the contacts — so check it sits flat before clicking the case shut.

My remote still won’t work with a fresh cell — now what?

Re-open it and check the cell orientation and that the contacts are clean. If it’s still dead, the fob may have an internal fault and need replacing and programming by a dealer or locksmith.

To clear a service reminder after maintenance, see our Mazda 2 service indicator reset guide. For warning lights, look up the code on autodtcs.com.