These instructions apply to the BMW X3 Mk3 (G01) 2017-Present.
For other models, please choose your vehicle here.
The BMW X3 (G01, 2017–present) has Auto Start-Stop, which switches the engine off at a standstill to save fuel and restarts it as you release the brake. The small ‘A’ that lights when the engine cuts is the system working normally, not a warning. If you’d rather keep the engine running — in traffic, on a hot day, or before working under the bonnet — you switch it off with one button.
How Auto Start-Stop Works on the X3
The G01 only shuts the engine off once several conditions are met: the car is fully stopped with your foot on the brake, the engine is at operating temperature, the 12 V battery has adequate charge, and the cabin climate demand is satisfied. An intelligent battery sensor monitors the state of charge so the system never risks a failed restart. When any condition isn’t met — or in some sport-oriented drive settings — the X3 simply keeps idling. That is why auto-stop can act at one junction and not the next.
Getting Ready
- You can press the button with the ignition on or the engine running — no need to be moving.
- Locate the AⓇ switch near the start/stop button or gear selector before you set off.
- 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 unless the default has been changed by coding — there is nothing to save.
How to Turn Off Auto Start-Stop
- Find the AⓇ (A with a circular arrow) button near the start/stop button or gear selector.
- Press it once — the indicator confirms Auto Start-Stop is off, and the engine will keep running when you stop.
It Resets Every Drive
Like nearly every car with this feature, the X3 re-enables Auto Start-Stop each time you switch the ignition off and on. There is no owner ‘off’ setting that sticks from the factory — press the button once per journey if you don’t want it. Some owners have the default changed via coding so it stays off, but that is a workshop job, not a menu toggle.
If the Engine Won’t Auto-Stop
If auto-stop has gone quiet even with the system switched on, check the everyday reasons before suspecting a fault:
- A weak or ageing 12 V battery — the most common cause. Short trips leave it under-charged, and the system holds the engine running to protect the restart.
- The cabin isn’t at temperature — strong heating or cooling demand keeps the engine turning until the interior settles.
- A cold engine — in the first minutes after a cold start the coolant is below the threshold, so no auto-stop.
- You’re not fully stopped or brake pressure is light — come to a firm halt with steady pedal pressure.
- Sport mode or a very short stop — some drive settings hold the engine on, and 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.
What Happens Next
With Auto Start-Stop switched off, the indicator shows the crossed-out state and the engine idles normally at every stop for the rest of the trip. Nothing else changes — fuel use is slightly higher in town, but stop-go driving is smoother. When you next start the car, the system quietly switches itself back on.
Frequently Asked Questions
How do I turn off Auto Start-Stop on a BMW X3?
Press the AⓇ button near the start/stop switch or gear selector. The indicator confirms the system is off, and the engine will keep idling at every stop until you next switch the car off. It is a single press — there is no press-and-hold needed.
Can I disable it permanently?
From the factory it resets to on each drive, so the simplest approach is to press the button at the start of every journey. The default on/off state can be altered with a coding change, but that is a workshop procedure rather than an owner menu setting, and it may not be reversible without the same equipment.
Why did it come back on by itself?
It re-enabled when you last switched the ignition off and on. The button only controls the current drive cycle, so after any stop where you turned the car fully off, Auto Start-Stop returns to its default on state ready for the next trip. Nothing has gone wrong.
Why won’t the engine stop at junctions even with it on?
The X3 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, a weak 12 V battery, or a sport drive setting will all hold the engine running. That is normal protective behaviour.
Does turning it off harm the engine or use more fuel?
No harm at all — 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 Auto Start-Stop only acts while you are stationary.
Could a warning light mean the system has failed?
If you see a dedicated start-stop fault message rather than the normal indicator, a tired 12 V battery is the usual cause — it 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 a start-stop fault light shows instead of the normal indicator, a tired 12 V battery is the usual cause — see our X3 battery guide.
Independent guide — not affiliated with BMW. Always follow your official service manual and safety precautions. Read our full disclaimer.