These instructions apply to the Hyundai Santa Fe Mk4 (TM) 2018-2023.
For other models, please choose your vehicle here.
The Hyundai Santa Fe Mk4 (TM, 2018–2023) has an Idle Stop & Go (ISG) system that switches the engine off at a standstill to save fuel and restarts it as you pull away. The green ‘A’ that appears when the engine cuts is the system working as designed, not a fault. If you’d rather keep the engine running — in traffic, on a hot day, or before working in the engine bay — you switch ISG off with one button.
How ISG Works on the Santa Fe
ISG only stops the engine once several conditions line up: the car is fully stopped with your foot on the brake, the engine is at operating temperature, the 12 V battery has enough charge, and the cabin climate demand is met. A battery sensor watches the state of charge so the system never leaves the larger Santa Fe unable to restart. When any condition isn’t satisfied, it simply keeps idling — so it is normal for auto-stop to work at one stop and skip the next depending on temperature, battery state, and how hard the heater or air-conditioning is working.
First, a Few Checks
- You can press the button with the ignition on or the engine running — no need to be moving.
- Locate the ‘A OFF’ switch first so you aren’t hunting for it in traffic.
- Switching it off for engine-bay work? Do it before you open the bonnet so the engine can’t auto-restart.
- The setting is per-journey — there is nothing to save.
How to Turn Off Idle Stop & Go
- Find the ‘A OFF’ (ISG) button on the dashboard, usually near the steering wheel or the switch bank.
- Press it once — the indicator confirms ISG is off, and the engine will keep running when you stop.
It Resets Every Drive
Like nearly every car with this feature, the Santa Fe re-enables ISG each time you switch the ignition off and on. There is no permanent factory ‘off’ — press the button once per journey if you don’t want it.
If the Engine Won’t Auto-Stop
If auto-stop has gone quiet even with ISG switched on, run through the everyday reasons before assuming a fault:
- A tired or ageing 12 V battery — the most common cause. A heavy vehicle draws hard on start-up, and short trips leave the battery under-charged, so the system holds the engine running to protect it.
- The cabin isn’t at temperature — strong heating or cooling demand, common in a large cabin, keeps the engine turning until the interior settles.
- A cold engine — on the first minutes of a cold morning the coolant is below the threshold, so no auto-stop.
- You’re not fully stopped or brake pressure is light — roll to a firm halt with steady pressure on the pedal.
- Steep gradient or a very short stop — the system may skip a stop it judges pointless.
- A recent battery disconnect — the sensor needs a few charge cycles to relearn the battery’s state.
Once It’s Done
With ISG switched off, the green ‘A’ changes to the crossed-out ‘A OFF’ indicator and the engine idles normally at every stop for the rest of the trip. Nothing else changes — fuel economy is slightly worse in town, but stop-go driving is smoother. Next time you start the car, ISG quietly switches itself back on.
Frequently Asked Questions
How do I turn off auto stop/start on a Hyundai Santa Fe?
Press the A OFF (ISG) button on the dashboard, usually near the steering wheel or in the switch bank. The dash indicator changes to confirm the system is off, and the engine will keep idling every time you stop until you next switch the car off.
Can I disable ISG permanently on the Santa Fe?
No. There is no menu setting or button hold that makes the ‘off’ state stick — ISG resets to on at every ignition cycle by design. The only workaround is to press the button once at the start of each journey. Many owners make it a habit right after starting the engine.
Why did ISG come back on by itself?
It didn’t switch on mid-drive — it re-enabled when you last turned the ignition off and on. The button only controls the current journey, so after any stop where you turned the car fully off, ISG returns to its default on state ready for the next trip.
Why won’t the engine stop at junctions even with ISG on?
The Santa Fe only auto-stops when the battery has charge, the engine is warm, and the cabin climate demand is met. A cold engine, a hot or cold cabin still being brought to temperature, or a weak 12 V battery will all hold the engine running. On a vehicle this size the battery and climate loads are higher, so this is common — and normal.
Does turning ISG off harm the engine or use more fuel?
It does no harm — the engine simply idles as any older car would. You may see marginally higher fuel use and emissions in stop-start traffic, but on the open road there is virtually no difference, because ISG only acts when you are stationary.
Could a warning light mean the ISG system has failed?
If you see a dedicated ISG fault message rather than the normal green indicator, the usual culprit is a 12 V battery that can no longer support a restart. Have the battery and its sensor checked first. If a stored trouble code is present, you can look it up on autodtcs.com.
If an ISG fault light shows instead of the normal indicator, a tired 12 V battery is the usual cause — see our Santa Fe battery guide.
Independent guide — not affiliated with Hyundai. Always follow your official service manual and safety precautions. Read our full disclaimer.