Start the Car With a Dead Key Fob Battery

Last updated: June 10, 2026

The SEAT Arona (KJ7, 2018–Present) shares its KESSY keyless system with the Ibiza it is based on, so on FR, Xcellence and FR Sport trims a dead key-fob battery normally locks you out of both the doors and the start button. It only feels like a dead end, though — the fob still holds a passive transponder that needs no power, and the Arona has an emergency reader built into the steering column. Open the door with the hidden blade, hold the fob to that spot, and the crossover starts.

This guide covers the SEAT Arona small SUV on the MQB-A0 platform. Lower-trim Aronas with a conventional turn-key barrel and a start button are simpler still: the cut blade in the fob turns the ignition directly, so a flat coin cell only affects the remote-locking buttons, never your ability to drive.

Start the keyless Arona with a dead fob

1. Sit in the driver’s seat with the fob and close the door so the cabin antenna can detect the key.
2. Press and hold the brake pedal — without it the Arona will not start.
3. Press the START/STOP button once; the cluster reports that no key was found.
4. Hold the fob flat against the right-hand trim of the steering column, beside the small KESSY logo just under the wiper stalk. The emergency antenna sits behind that point, where a lock cylinder would be on a non-keyless car.
5. Keep the fob there and press START/STOP again with the brake held. The immobiliser reads the passive chip and the engine starts.

Unlock the doors with the emergency key blade

1. Slide the catch on the fob and withdraw the metal emergency blade.
2. On the driver’s door handle, insert the blade tip into the slot beneath the lock cover and lever the cover off upward to reveal the lock cylinder.
3. Turn the blade to unlock the door. The alarm may sound — it stops once you start the car.
4. Press the handle cover back into place over the lock.

Why this works — the immobiliser note

The Arona’s smart key contains a battery-powered radio for keyless entry and a passive RFID transponder powered wirelessly by the car. The coin cell only feeds the radio half, so when it dies the keyless convenience stops but the transponder still answers the immobiliser whenever it is held within a few centimetres of the KESSY antenna. The steering column is the one place in the cabin guaranteed to be close enough, which is why the engine starts there.

Replace the fob battery

The Arona fob takes a single CR2032 3V lithium coin cell as standard. Pull out the emergency blade, split the fob at the seam it exposes, lift out the old cell and fit the new one with the + face up, then clip it shut. Because the car and key constantly poll one another, keyless Aronas can flatten a fob in well under a year — owners often report nine to twelve months even on a good battery, so keep a spare cell in the glovebox.

Frequently Asked Questions

Where is the KESSY reader on the Arona? On the right side of the steering column under the wiper stalk, marked with a small Wi-Fi-style icon. Hold the fob there after the first button press.

How long should the Arona fob battery last? On a keyless car, often only nine to twelve months because the key and car poll each other constantly. A non-keyless Arona’s fob lasts far longer.

Does the Arona fob take a CR2032 or CR2025? The Arona is fitted with a CR2032 as standard. Always check the cell you remove, as the slimmer CR2025 will sit loose and cause “key not found” faults.

The car started but won’t lock remotely — why? Remote locking needs the fob’s radio, which the dead cell powers. Lock the door with the blade until you fit a new battery.

Is it safe to keep driving on a dead fob? Yes — once started, the engine keeps running. Just don’t switch off in an awkward spot, as you will need the steering-column trick again to restart.

If a warning light or fault code showed alongside the key message, you can look it up on our sister site autodtcs.com.