These instructions apply to the SEAT Leon Mk4 (KL) 2020-present.
For other models, please choose your vehicle here.
Your SEAT Leon (KL, 2020–present) shuts the engine off at a standstill to save fuel and trim emissions. When you’d rather it didn’t — crawling in stop-start traffic, on a hot day when you want steady cooling, or before any under-bonnet work — one button switches it off. The feature is entirely normal: the “A” symbol in the cluster is a status light, not a fault warning.
How Start/Stop Works on the Leon
Auto Start/Stop is managed by the car, not just the button. When you come to a halt and hold the brake, the engine cuts only if a set of conditions are met — the 12 V battery has enough charge, the engine has reached operating temperature, the cabin climate demand is satisfied, and the car is on reasonably level ground. Lift off the brake (or dip the clutch on a manual) and it fires straight back up. Because the system watches battery state of charge closely, a tired battery is the single most common reason the engine simply won’t stop.
First, a Few Checks
- Have the ignition on and the engine running — the button only acts on a live system.
- Decide before you set off: the setting resets each time you restart the car.
- For engine-bay work, switch it off first so the engine can’t auto-restart while your hands are near belts or the fan.
- Locate the button near the gear lever before you pull away, so you’re not hunting for it while moving.
Turning Start/Stop Off
- Locate the AⓇ button (an “A” circled by an arrow), usually near the gear lever.
- Press it once; the indicator confirms the system is off and the engine stays running at stops.
Why It’s On Again Next Time
The Leon switches Start/Stop back on at every ignition cycle — there’s no permanent off from the factory. Tap the button once at the start of each drive if you don’t want it.
If the Engine Won’t Cut (Or Won’t Stay Off)
If you expect the engine to stop at a light and it keeps running — even with Start/Stop enabled — run through these before assuming a fault:
- Cold engine. On the first few minutes of a cold start the system waits until coolant temperature comes up.
- Weak or ageing 12 V battery. The most frequent cause; low state of charge inhibits the stop to protect restart ability. An AGM/EFB battery near the end of its life behaves the same way.
- Heavy climate demand. Full heating or air-con on a very hot or cold day keeps the engine turning to run the compressor and heater.
- Gradient or not fully stopped. On a slope, or if the car is still creeping, it holds the engine on.
- Steering or seatbelt inputs. Turning the wheel at a standstill or an open door/undone belt can block the stop.
- Setting keeps re-arming. That’s by design — it can’t be saved off permanently, so press the button each drive.
Once It’s Done
With Start/Stop switched off, the indicator shows the function is disabled and the engine idles normally at every stop for the rest of that drive. There’s no lasting effect on the car — next time you start up, the system is armed again and behaves exactly as before. Leaving it on does no harm; the engine simply cycles off and on at stops, which is what it’s designed to do.
Frequently Asked Questions
How do I switch off auto Start/Stop on a SEAT Leon?
Press the AⓇ button near the gear lever once, with the engine running. The cluster indicator confirms the system is disabled, and the engine will idle rather than cut out at the next stop. You’ll need to repeat this each time you drive, because the setting doesn’t carry over.
Can I turn it off permanently?
Not from the factory settings — the Leon re-arms Start/Stop every time you start the engine, so there’s no menu toggle to keep it off for good. The only way to disable it for a journey is the button. If it genuinely bothers you long term, an independent specialist can sometimes recode the default, but that’s outside the standard controls.
Why did it switch itself back on?
Cycling the ignition off and on resets the function to its default enabled state. This is normal behaviour, not a fault. Simply press the AⓇ button again at the start of the next drive if you want it off.
Why won’t the engine stop at lights sometimes?
The car only stops the engine when several conditions line up: a healthy 12 V battery, warm engine, satisfied cabin climate, and a level, fully stationary car. If the battery is low, the engine is still warming up, or the air-con is working hard, it keeps running by design to protect the battery and your comfort.
Is it bad to leave Start/Stop on?
No. The system and the starter are built for frequent cycling, and leaving it enabled saves a little fuel in town driving. Many owners simply leave it on and only disable it in specific situations — heavy traffic, extreme weather, or before working under the bonnet.
Could a warning symbol mean my battery is failing?
Often, yes. If a Start/Stop fault symbol appears or the engine consistently refuses to stop, a weak or ageing 12 V battery is the usual culprit. Have the battery’s state of charge and health tested; replacing a tired battery frequently restores normal Start/Stop operation.
If a start/stop fault symbol shows, it usually points to a weak 12 V battery — see our Leon battery guide, or look the code up on autodtcs.com.
Independent guide — not affiliated with SEAT. Always follow your official service manual and safety precautions. Read our full disclaimer.