pre collision sensor question

[shex777799]

Hi all, I am new here. Just curious on one feature that the pre collision function, I been driving this 2016 640xi gc for 3 months but only had it alert me once. Was seeing paint covering one front radar sensors rubber ring so maybe that sensor is not functioning well? The real question is which sensor does it use for pre collision, radar or camera on the windshield? Thanks guys!

[Opie55]

Windshield camera. It triggers in stages. The first thing you get is just a red car outline in your cluster. That's if you get too close and it does not not sense you braking - i.e., you are closing on the car in front. Eventually your car will brake for you, but not until just before you crash. The bumper sensors are just for parking. They are not even on unless you first put the car in reverse.

[shex777799]

Originally Posted by Opie55

Windshield camera. It triggers in stages. The first thing you get is just a red car outline in your cluster. That's if you get too close and it does not not sense you braking - i.e., you are closing on the car in front. Eventually your car will brake for you, but not until just before you crash. The bumper sensors are just for parking. They are not even on unless you first put the car in reverse.

Thanks! Yeah I saw a red car icon on the cluster that time and it was kind of close but not very close. I set the distance level to far for the pre collision and I had other situations that I went closer to car in front but nothing triggered. Maybe because I was breaking. Its just not as sensitive as my previous mb car's so I am a little worried. Guess no biggy?

[Opie55]

Originally Posted by shex777799

Thanks! Yeah I saw a red car icon on the cluster that time and it was kind of close but not very close. I set the distance level to far for the pre collision and I had other situations that I went closer to car in front but nothing triggered. Maybe because I was breaking. Its just not as sensitive as my previous mb car's so I am a little worried. Guess no biggy?

Sounds like it's working correctly. You can get as close as you want if your are braking. I'm sort of a late, hard braker but it never triggers unless I am going faster than the car ahead and am not braking yet.

[shex777799]

Originally Posted by Opie55

Sounds like it's working correctly. You can get as close as you want if your are braking. I'm sort of a late, hard braker but it never triggers unless I am going faster than the car ahead and am not braking yet.

Thanks again! This makes a lot sense to me on the relative speed and braking thing. I can say now just difference on mb and bmw lol.

[Qsilver7]

Also...there may be an embedded video in your iDrive's owners manual that may help explain how the system works.

If you only have the city mitigation & pedestrian collision features...then it only works between certain speeds and conditions.

If you are a pretty safe driver, then you won't see the warnings unless you are in close calls of a collision. As Opie55 has already mentioned, the warning has TWO stages. The first only gives a visual (red car) warning. The ACUTE warning is visual & audible...and again will prep the brakes for stopping...but if you are moving between 6 MPH-37 MPH....plus moving faster than the vehicle in front of you, then it will begin to brake for you but you still need to react and brake, too.

Again, I think you should look to see if you have an embedded video that shows how the system works. It shouldn't be hard to find in the iDrive's owners manual...do a keyword search for "animated explanations". Or if there aren't any videos...then do a search for city mitigation which should discuss the parameters of the two warnings and the iDrive owners manual will only cover the features that are optioned on the car.

If you have ACC (auto cruise control) then you will not only have the KAFAS camera...but a radar sensor installed in the lower front grille. If you do not have ACC...then only the KAFAS camera facilitates city mitigation/braking.

Here's some examples of what you may find under animated explanations:









And here's a video found on youtube:

[shex777799]

Originally Posted by Qsilver7

Also...there may be an embedded video in your iDrive's owners manual that may help explain how the system works.

If you only have the city mitigation & pedestrian collision features...then it only works between certain speeds and conditions.

If you are a pretty safe driver, then you won't see the warnings unless you are in close calls of a collision. As Opie55 has already mentioned, the warning has TWO stages. The first only gives a visual (red car) warning. The ACUTE warning is visual & audible...and again will prep the brakes for stopping...but if you are moving between 6 MPH-37 MPH....plus moving faster than the vehicle in front of you, then it will begin to brake for you but you still need to react and brake, too.

Again, I think you should look to see if you have an embedded video that shows how the system works. It shouldn't be hard to find in the iDrive's owners manual...do a keyword search for "animated explanations". Or if there aren't any videos...then do a search for city mitigation which should discuss the parameters of the two warnings and the iDrive owners manual will only cover the features that are optioned on the car.

If you have ACC (auto cruise control) then you will not only have the KAFAS camera...but a radar sensor installed in the lower front grille. If you do not have ACC...then only the KAFAS camera facilitates city mitigation/braking.

Here's some examples of what you may find under animated explanations:









And here's a video found on youtube:

big thumb up! Thanks for all the comments, I will check the videos.

[Qsilver7]

Here’s an example of the info direct from the embedded owners manual in iDrive as to the auto braking/city mitigation feature:

[shex777799]

Originally Posted by Qsilver7

Here’s an example of the info direct from the embedded owners manual in iDrive as to the auto braking/city mitigation feature:

Thanks again Q! I had one warning on hud once more today on a freeway so it works!

[Qsilver7]

[Everything Auto NY]

I definitely wouldn't compare it to the MB precollision. The MB one is hyper sensitive and engages even if you are braking already

[shex777799]

Originally Posted by Everything Auto NY

I definitely wouldn't compare it to the MB precollision. The MB one is hyper sensitive and engages even if you are braking already

yes mbs is sensitive but Id say sometimes it should help you to tell if your braking hard enough.