In this article, I will explain the common causes and solutions for a malfunctioning BMW auto start stop system. Lets get into it!
BMW Auto Start Stop System: A Simple Breakdown
As automotive technology continues to advance, manufacturers like BMW have developed innovative new features to improve fuel efficiency and reduce emissions.
One such feature is BMW’s Auto Start-Stop system, which automatically shuts off the engine when your vehicle comes to a stop and then simply restarts it when you release the brake or turn the steering wheel.
The Auto Start-stop helps conserve fuel that would otherwise be wasted idling during your stops.
This smart tech senses when you’ve come to a stop, like at a light or in a jam. As soon as you hit the brakes, it switches off the engine to save gas.
When the brake is released, the engine restarts in an instant. So you can glide back into motion without any delay.
The Start-Stop makes those annoying stops less of a grind. Your drive is now seamless, saving fuel and reducing emissions along the way.
By avoiding unnecessary idling, BMW’s Auto Start-Stop technology reduces your fuel consumption and decreases your harmful emissions.
Conditions that Need to Be Met For Your BMW Start Stop to Function Properly
Now that I have briefly explained how this system works, there are certain conditions that need to be met for the system to function properly.
Here are some of the most important ones:
Good Battery Condition and Voltage:
The most important condition that needs to be met is a good battery condition and voltage.
Your BMW’s battery must be in good condition and have sufficient voltage.
If your car does not have a weak or dead battery, then this is not the cause of your Start-Stop issues.
Your BMW Engine Temperature Must be in Operating Temperature:
The second condition that needs to be met in order for your start stop system to work is that your BMW engine must be at operating temperature.
If the engine is still cold and hasn’t reached operating temperature, then the start stop system will not work.
Outside Temperature:
Yes, it’s true that the auto start stop system is also influenced by the temperature outside.
The outside air temperature also factors into whether the BMW Auto Start-Stop system activates. The system has minimum and maximum temperature thresholds that must be met.
The system works best when the temperature outside is between 0°C (32°F) and 30°C (86°F) Fahrenheit.
If it is below this range, then the start stop system will not work properly.
Here is an expanded explanation of those two conditions:
Steering Angle Must Be Straight:
The BMW Auto Start-Stop system requires that the steering wheel is in the straight-ahead position when the vehicle comes to a stop.
This means the front wheels must be pointed straight, and the steering angle is neutral.
If the steering wheel is turned to either side, the system will not automatically shut off the engine.
This steering angle requirement exists because the auto start-stop is designed to activate only when the vehicle is completely stationary and in a stable, idling condition.
If the steering wheel is turned, the vehicle could begin moving again just from the wheels rolling slightly. The system avoids unnecessarily shutting off the engine if steering input is detected.
Essentially, the wheels have to be centered for the system to engage.
Driver’s Seatbelt Must Be Fastened:
Another condition the BMW Auto Start-Stop system requires is that the driver must have their seatbelt buckled.
The vehicle monitors the seatbelt sensor to confirm the belt is fastened before it activates the auto start-stop feature.
The system will not automatically shut off the engine if it detects the driver is unbuckled.
This prevents the engine from stopping and leaving the vehicle without powered systems while occupants are unrestrained.
Having the seatbelt buckled provides confirmation that the driver is indeed intentionally stopped with the vehicle in a secure state.
BMW Start Stop Problems Troubleshooting Table
| Issue | Possible Causes |
|---|---|
| Engine does not automatically shut off when stopped | 1. Driver’s seatbelt not fastened 2. Vehicle not completely stopped 3. Transmission not in neutral/drive gear 4. Clutch pedal depressed 5. Steering wheel being turned 6. Engine not warmed up 7. Vehicle battery significantly discharged 8. Hood unlocked 9. Driving in reverse recently 10. Windshield fogging up |
| Engine does not automatically restart | 1. Transmission not in neutral/drive gear 2. Clutch pedal not depressed 3. Steering wheel not turned 4. Brake vacuum too low 5. Vehicle battery charge too low 6. Windshield fogging up 7. Passenger compartment too hot/cold |
| Frequent unexpected start/stop cycles | 1. Stop-and-go traffic 2. Steering wheel adjustments at stops 3. Aggressive braking patterns |
| System disabled | 1. Driver’s seatbelt unbuckled 2. Hood opened 3. System fault detected 4. Vehicle battery changed/disconnected |
Why is Your BMW Auto Start-Stop Not Working?
Now that you know the factors that influence your BMW start stop system.
Let us now look at the most common causes of the system not working.
1. Bad Battery:
Here’s one way to rewrite that: In my time servicing BMWs, I’ve found the Auto Start-Stop system is super sensitive to battery condition.
This fuel-saving tech needs strong voltage – at least 80% capacity – to activate. But when the battery starts fading, stop-start stops working.
A weak or old battery is behind 90-95% of non-functioning cases I see. The system relies on robust energy to seamlessly shut off and restart the engine. Without it, Auto Start-Stop gets tripped up.
So if your stop-start stalls out, the issue likely lies with low battery power. A replacement restores the smooth functionality and gets those mpgs maximized once again. Proper voltage is key to keep Auto Start-Stop’s operation tip-top.
2. Your Engine is Still Cold:
The second common reason the Auto Start-Stop system doesn’t work is because the engine is still cold.
The engine needs to be above a certain temperature for the stop start function to activate and begin operating.
You may need to drive a few miles/KM before your engine is warm enough for the Auto Start-Stop system to begin working.
3. Accidently Pressed the Auto Start Stop Off Button:
Sometimes, the Auto Start-Stop system doesn’t work because you accidentally pushed the button to turn it off.
When this happens, you it won’t work until you reactivate it.
4. Outside Weather is too Cold/Hot:
The fourth and final reason why your BMW Start Stop feature may not be working is because of the outside weather.
As I mentioned above, the system needs to be above a certain temperature for it to work.
How to Get Your BMW Auto Start-Stop System Working Again
Lastly, let’s look at the things you can do to fix the stop start system on your Bimmer.
Here is what I personally recommend:
- Get the Battery Checked and Replaced/Charged if needed (This should fix the issue)
- Ensure that there are no other faults in your BMW
- Make sure that the “Auto start stop off” button is not On
- Warm Up your Engine before Driving.
Additional Sources:
https://www.bmwoftenafly.com/service/service-tips-tricks/bmw-automatic-start/
https://www.bimmer-tech.net/blog/item/131-bmw-auto-start-stop