These instructions apply to the Hyundai i20 Mk3 (BC3) 2020-Present.
For other models, please choose your vehicle here.
Your Hyundai i20 Mk3 (BC3, 2020–present) has an Idle Stop & Go (ISG) system that switches the engine off when you stop to save fuel. If you’d rather keep it running in traffic, it’s one button to turn off. Here’s how, and why it sometimes won’t cut the engine.
How ISG Works on the i20
Stop, select neutral and release the clutch (manual) or brake to a halt (auto), and the engine shuts off; dip the clutch or lift the brake and it restarts. It only operates once the engine is warm and the battery is healthy. The 48 V mild-hybrid i20 restarts especially smoothly.
How to Switch It Off
- With the engine running, press the ISG / Auto Stop OFF button — an “A” inside a circular arrow (with OFF), in the button panel on the lower dash, left of the steering wheel (next to the headlight-leveling dial and the heated-wheel / ESC-off buttons; see photo above).
- The light inside the button comes on to confirm ISG is off, and the engine now idles normally at a stop.
How to Switch It Back On
Press the button again, or simply restart the car — ISG defaults back on every time you switch the ignition off and on.
Hyundai lists several conditions that must all be met before ISG will cut the engine. The usual reasons it stays running:
- The engine isn’t up to operating temperature yet.
- The battery charge is low — common after a battery change or short trips; ISG is blocked to protect the battery.
- The driver’s seat belt isn’t fastened, or the driver’s door or bonnet is open. Any of these keeps ISG from stopping the engine — and if the engine had already auto-stopped, unbuckling or opening the door restarts it.
- Cabin heating, cooling or demisting still needs the engine running.
- The outside temperature is very low or very high.
- The steering is turned sharply, the car is on more than a gentle slope, or you haven’t driven above walking pace since the last stop.
If ISG stopped working after a battery change, let the battery fully charge — see our i20 Mk3 battery guide.
Frequently Asked Questions
Does the i20 remember my ISG setting?
No — it resets to on at every start. There’s no built-in option to keep it off.
Is it bad to keep using ISG?
No — the i20’s reinforced starter and battery are designed for it, and it skips stops when the battery is low.
Why won’t the engine auto-stop?
Most often a cold engine, a low battery, or the climate system demanding the engine.
The ISG warning light is on — what now?
A lit ISG fault usually points to battery condition or a bonnet/seat-belt switch; have it read if it persists.
If a warning light appeared alongside the fault, look up the code on autodtcs.com. To clear a service reminder, see our i20 Mk3 service reset guide.
Independent guide — not affiliated with Hyundai. Always follow your official service manual and safety precautions. Read our full disclaimer.