Start the Car With a Dead Key Fob Battery

Last updated: June 10, 2026

The SEAT Ateca (5FP, 2016–Present) was SEAT’s first SUV and one of its earliest cars to offer KESSY keyless go, so a dead key-fob battery is a common gripe on owner forums — the doors ignore the handle and the start button stays dark. It is not a breakdown, though. The fob keeps a battery-free transponder, and the Ateca hides an emergency reader in the steering column. Let yourself in with the blade, hold the fob to that spot, and the SUV starts normally.

This guide covers the SEAT Ateca on the MQB platform, including the facelift. Lower-trim Atecas without keyless go use a conventional turn-key barrel with a start button; on those the cut blade turns the ignition directly, so a flat coin cell only disables the remote-locking buttons and never stops you driving.

Start the keyless Ateca with a dead fob

1. Climb into the driver’s seat with the fob and shut the door so the interior antenna can work.
2. Press and hold the brake pedal firmly — the Ateca refuses to start without it.
3. Press the START/STOP button once. The dash shows a “key not detected” warning.
4. Hold the fob flat against the right-hand trim of the steering column, right against the small Wi-Fi-style KESSY symbol below the wiper stalk. The emergency antenna is behind that point, where a lock cylinder would sit on a non-keyless car.
5. Keeping the fob pressed there, push START/STOP again with your foot still on the brake. The chip is read through the antenna and the engine starts.

Unlock the doors with the emergency key blade

1. Slide the catch on the fob and pull out the metal emergency blade.
2. Insert the blade into the lower opening of the cover on the driver’s door handle and lever the cover off upward to expose the lock cylinder.
3. Turn the blade to unlock the door. Do this within about a minute of pressing the (non-working) unlock button if you can, and expect the alarm to sound — it stops once you start the car.
4. Refit the handle cover over the lock afterwards.

Why this works — the immobiliser note

The Ateca’s smart key holds a battery-powered radio for keyless entry plus a passive RFID transponder that the car powers wirelessly through its antenna coil. A dead coin cell only kills the radio; the transponder still answers the immobiliser when held within a few centimetres of the KESSY reader. That is why bringing the fob to the steering column — the nearest point to the coil — lets the engine start even when remote unlocking has stopped working.

Replace the fob battery

The Ateca fob uses a CR2025 3V lithium coin cell — note this is the thinner cell, not the CR2032 some other SEATs take, so check the printed code before buying. Pull out the emergency blade, split the fob at the seam, swap the cell with the + face up and clip it shut. Owners report roughly twenty months on a good branded battery, though KESSY’s constant polling means some get far less; a cheap cell will trigger the low-battery warning much sooner.

Frequently Asked Questions

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

Does the Ateca fob take a CR2032 or CR2025? The Ateca uses the thinner CR2025. Fitting a CR2032 won’t close the case, and a loose CR2025 substitute causes intermittent “key not found” faults — always match the original.

How long does the Ateca key battery last? SEAT dealers quote around twenty months, but heavy KESSY use shortens that. Carry a spare CR2025 if your fob is getting old.

My older Ateca has a turn-key — does this apply? No. Non-keyless Atecas start on the cut blade in the barrel, so a dead fob only affects remote locking, not starting.

The alarm sounded when I opened the door — is that a fault? No, it is by design when you use the mechanical blade. It silences the moment the car recognises the key and starts.

If a warning light or fault code appeared with the key message, you can decode it on our sister site autodtcs.com.