Replace the Key Fob Battery

When the remote key’s range drops off or the lock and unlock buttons stop responding, the coin cell inside the fob has usually gone flat. Swapping it takes a couple of minutes and needs no special tools. The remote keeps its pairing, so there is no reprogramming to do afterwards.

1. If the remote is built into the key, fold or pull out the mechanical key blade first so it is clear of the case.
2. Insert a small flat screwdriver into the seam between the two halves and gently prise the case apart. Do not use excessive force, and avoid touching the circuit board or the metal terminals.
3. Lift out the old coin cell, noting which way up it sits.
4. Check the marking on the old cell for the exact type before buying a replacement — these small Toyota remotes typically take a CR1620 or CR2016. Fit a fresh cell of the same type with the positive (+) side facing upwards.
5. Press the two halves of the case back together until they clip shut, then refit the key blade. Press a button to confirm the remote locks and unlocks the car.

Good to know

A flat remote does not leave you stranded. The cut mechanical key still unlocks the door and starts the engine, so you can drive as normal while you sort out a replacement cell.

Because the battery only powers the remote’s radio circuit, changing it does not affect the pairing with the car. There is nothing to initialise or programme afterwards.

FAQ

What battery does the Aygo key take?

A small coin cell. Check the marking stamped on the old cell before buying, as it is the surest guide — on these first-generation Aygo remotes it is commonly a CR1620 or CR2016.

Which way up does the battery go?

Positive (+) side upwards, matching the way the old cell sat in its holder.

Do I need to reprogramme the key after changing the battery?

No. A battery change does not unpair the remote, so it works straight away with no reprogramming.

The remote still does not work after a new battery — what now?

Recheck the cell is the right way up and that it is seated properly, and wipe the contacts clean. If it still fails to respond, the remote itself may be faulty and will need dealer attention.