These instructions apply to the BMW 3 Series Mk7 (G20) 2019-Present.
For other models, please choose your vehicle here.
Your BMW 3 Series Mk7 (G20, 2019–present) has Auto Start-Stop, which switches the engine off at a standstill to save fuel. If you’d rather keep it running, it’s a quick button press to turn off. Here’s how, and why it sometimes won’t cut the engine.
How It Works on the G20
Brake to a stop (automatic) or stop, select neutral and release the clutch (manual), and the engine shuts off; lift the brake or dip the clutch and it restarts. The mHEV models restart especially smoothly via the 48 V starter-generator. It only operates once the engine is warm and the battery is healthy.
How to Switch It Off
- With the engine running, press the Auto Start-Stop button — the “A” inside a circular arrow, near the start/stop button or on the centre console.
- A dash light confirms it’s disabled, and the engine idles normally at a stop.
On some G20s you can set a preference in iDrive (e.g. via the driving-experience/ECO settings), but the button is the quick way.
How to Switch It Back On
Press the button again, or simply restart the car — Auto Start-Stop defaults back on every time you switch the ignition off and on.
Why It Sometimes Won’t Activate
- The engine isn’t warm yet, or the climate system is demanding heating/cooling/demist.
- The battery charge is low — common after short trips or a battery change before the new battery was registered; auto-stop is blocked to protect it.
- You’re on a slope, the steering is turned, or you haven’t fully stopped.
If it stopped working after a battery change, the new battery may need registering — see our 3 Series G20 battery guide.
Frequently Asked Questions
Does the G20 remember my Auto Start-Stop setting?
The button resets to on at every start. Some cars hold a preference set through iDrive, but the button itself is per-drive.
Is it bad to keep using it?
No — the G20’s reinforced starter (or 48 V system) and AGM battery are built for it, and it skips stops when the battery is low.
Why won’t the engine auto-stop?
Usually a cold engine, a low battery, or the climate system demanding the engine.
The light says it’s unavailable — is that a fault?
Often the battery is low or the engine isn’t warm; if it persists after a charge (and battery registration), have it checked.
If a warning light appeared alongside the fault, look up the code on autodtcs.com. To clear a service reminder, see our 3 Series G20 service reset guide.
Independent guide — not affiliated with BMW. Always follow your official service manual and safety precautions. Read our full disclaimer.