These instructions apply to the Toyota Corolla Mk12 (E210) 2019-Present.
For other models, please choose your vehicle here.
If the smart key on your Toyota Corolla Mk12 (E210, 2019–present) has gone weak — you have to be close to lock or unlock, or a “key battery low” message has appeared — the fob’s coin cell needs renewing. The Corolla key uses a CR2032 cell and opens with the help of the emergency key blade. This guide shows how, with no programming required.
What You Need
- One fresh CR2032 3 V lithium coin cell.
- The fob’s built-in mechanical key, plus a small flat screwdriver to release the cover.
How to Replace the Corolla Mk12 Key Battery
- Pull out the mechanical key — slide the release catch and withdraw it.
- Insert a small flat screwdriver into the slot the key leaves (or the case seam) and gently prise off the key cover.
- Lift out the old CR2032 cell, noting its orientation.
- Fit the new cell with the positive (+) side facing up (same way as the old one).
- Refit the cover and slide the mechanical key back in.
- Test lock/unlock and keyless entry from a normal distance.
Does It Need Programming?
No — renewing the coin cell does not affect the fob’s pairing, so the smart key keeps working straight away. A lost or broken key can only be ordered and coded by a Toyota dealer — that part isn’t owner-doable.
If It Still Won’t Respond
Re-open the fob and check the cell sits positive-up with clean contacts. If keyless entry is slow to pick up, touch the fob to the POWER/START button (Toyota marks the backup spot) to start, then it re-syncs.
Frequently Asked Questions
What battery does the Corolla Mk12 key take?
A single CR2032 3 V lithium coin cell.
Will the car still start if the key battery is flat?
Yes. Hold the smart key against the POWER/START button (Toyota marks the spot) to start using the backup transponder. The mechanical key unlocks the driver’s door.
Which way up does the cell go?
Positive (+) side facing up, matching the cell you removed.
Can I program a spare key myself?
No — Toyota key coding needs the dealer system. Only the battery swap is owner-doable.
To clear a maintenance reminder after a service, see our Corolla Mk12 maintenance reset guide. For warning lights, look up the code on autodtcs.com.
Independent guide — not affiliated with Toyota. Always follow your official service manual and safety precautions. Read our full disclaimer.