Replace the Key Fob Battery

Last updated: June 12, 2026

If the keyless remote on your Mazda CX-5 Mk2 (KF, 2017–present) is getting weak — short range, fussy keyless entry, or a “key battery low” message — the coin cell needs renewing. The CX-5 smart key takes a CR2032 and opens with the auxiliary key inside. No programming needed.

What You’ll Need

• A fresh CR2032 3 V lithium coin cell.
• The metal auxiliary key inside the fob, plus a small flat screwdriver.

How to Replace the CX-5 Mk2 Key Battery

1. Slide out the auxiliary (emergency) key — press the release and withdraw it.
2. Use a small screwdriver in the slot the key leaves to split the case and remove the cover.
3. Lift out the old CR2032, noting which way up it sits.
4. Fit the new cell the same way, by the edges.
5. Click the case together and slide the auxiliary key home.
6. Test lock/unlock and keyless entry from a normal distance.

Does It Need Programming?

No — the swap doesn’t affect the key’s pairing, so it works straight away. A lost or extra smart key can only be ordered and coded by a Mazda dealer.

If It Still Won’t Respond

Re-open the fob, check the cell orientation and clean the contacts. If keyless entry is slow, touch the fob to the START button to start, then it re-syncs.

Frequently Asked Questions

What battery does the Mazda CX-5 Mk2 key take?

A single CR2032 3 V lithium coin cell.

Will the car start with a flat key battery?

Yes — touch the smart key to the START button to start on the backup transponder; the auxiliary key unlocks the driver’s door.

Which way up does the cell go?

Match the orientation of the cell you removed.

Can I program a spare key myself?

No — Mazda key coding needs the dealer system. Only the battery swap is DIY.

To clear a service reminder after maintenance, see our CX-5 Mk2 service reset guide. For warning lights, look up the code on autodtcs.com.