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      08-12-2018, 01:05 PM   #1
abcsoup
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Exclamation False Positive Emergency Auto Braking

Today, our X3 activated the emergency braking system when there was nothing in front of us. This occurred after the stoplight turned green (we were the first car at the light) and we were accelerating up to speed (maybe 40 mph or so). Suddenly, the car beeped and showed the red flashing icon of a collision warning, it moved the seats up, tightened the belts, and slammed on the brakes. Fortunately for us, the car behind us was paying attention and we didn't get rear-ended, but it was very frightening. Once the system reacts, you can do nothing to stop it.

The collision warning setting in the car was set to Medium, and the car was quite clean as I checked the sensors and windshield for any dirt/dust. Has anyone else experienced this in their car? I have found a couple threads with other BMWs in which drivers experienced false positives:

https://f87.bimmerpost.com/forums/sh....php?t=1454733 (M2)
https://g30.bimmerpost.com/forums/sh....php?t=1403100 (5 series)

My vehicle has all the assistance packages (parking and driver) with adaptive cruise control, and things had worked flawlessly until today.

I think I will have to bring it into the dealer to get the sensors checked and possibly re-calibrated, but I'm left wondering if it is an issue with the collision sensing algorithm itself.

EDIT: Here is a link to the intersection that caused the false positive. I was in the left-most lane going south on Leesburg Pike. https://goo.gl/maps/Mt5T7n5vsTE2

Last edited by abcsoup; 08-12-2018 at 01:09 PM.. Reason: Added location of false positive
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      08-12-2018, 01:24 PM   #2
Pray for Mojo
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My M235i has done this twice in 70,000 km. Both times there was nothing there other than a dip in the road or a shadow.
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      08-12-2018, 05:42 PM   #3
abcsoup
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Quote:
Originally Posted by Pray for Mojo View Post
My M235i has done this twice in 70,000 km. Both times there was nothing there other than a dip in the road or a shadow.
I appreciate the info; in the meantime, I've set the collision warning to Early instead of Medium to hopefully get an earlier indication when this happens.
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      08-12-2018, 06:14 PM   #4
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      08-12-2018, 08:20 PM   #5
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nothing in front, but anything to the side (but ahead of you)? I've had my car detect people in the lane next to me if they get to close to the separation line. cruise control has slowed me down like someone has merged in front of me, but nobody does.

anything like that? aka just being super sensitive? or just possibly a glitch?
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      08-12-2018, 10:08 PM   #6
abcsoup
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Quote:
Originally Posted by Ragnarkov View Post
nothing in front, but anything to the side (but ahead of you)? I've had my car detect people in the lane next to me if they get to close to the separation line. cruise control has slowed me down like someone has merged in front of me, but nobody does.

anything like that? aka just being super sensitive? or just possibly a glitch?
I don't recall seeing anything to the side, as I was ahead of the pack shortly after the light turned green. Maybe it was some small debris in the road that reflected the radar sensors in just the right condition? The road is quite flat in that area, so no bumps to trigger it.

I wish BMW would record the sensor and camera data 30 seconds prior to each activation of the emergency system. It would be a helpful debugging tool, but it could get them in trouble. I'm thinking of installing a dashcam now specifically in case the emergency system triggers falsely again so I wouldn't be held liable if anything were to happen.
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