These instructions apply to the Hyundai i20 Mk2 (GB) 2014-2020.
For other models, please choose your vehicle here.
If your Hyundai i20 Mk2 (GB, 2014–2020) has the Smart Key system — the fob you keep in your pocket with an Engine Start/Stop button on the dash — a flat fob battery will stop it unlocking and starting the car normally. You can still get in and drive: the fob hides a mechanical key, and the start button reads the fob directly as a backup.
Does this apply to your i20?
This is only for cars with Smart Key / keyless start (an Engine Start/Stop button, no key you turn in a barrel). It applies to European and other-market (e.g. Indian Elite i20) cars so equipped. If your i20 uses an ordinary flip key you turn in the ignition, a flat remote just means no remote locking — you still start normally, so simply replace the key fob battery.
Unlock the car with a dead fob
- Slide the release catch on the Smart Key and pull out the mechanical emergency key inside.
- Use that key in the driver’s door lock to unlock the car. (The alarm may sound; it stops once you switch the ignition on.)
- Push the emergency key back into the fob.
Start the engine with a dead fob
- Press the brake pedal (automatic) or clutch pedal (manual) and hold it.
- Touch the Smart Key directly onto the Engine Start/Stop button — press the button with the fob itself. The button reads the fob’s transponder even when its battery is flat.
- With the pedal still pressed, the ignition switches on; press the Start/Stop button again to start the engine.
- Once running, replace the fob battery so keyless entry and start work again.
Frequently asked questions
Where is the mechanical key on the i20 Smart Key?
It is a slim blade stored inside the fob. Slide the small release button and it pulls straight out.
Why won’t the car detect my fob normally?
A flat fob battery cannot transmit at range, so the car cannot sense it passively. Holding the fob against the start button lets the backup reader pick up the transponder.
Is it the battery or something worse?
If a fresh coin cell restores normal operation, it was the battery. If the fob still will not work against the button, the transponder or Smart Key unit may need checking — look up any immobiliser warning on autodtcs.com first.
After fixing it, swap the coin cell using our i20 key fob battery guide.
Independent guide — not affiliated with Hyundai. Always follow your official service manual and safety precautions. Read our full disclaimer.