SCARY Active Brake Assist malfunction?
Thread Starter
MBWorld Fanatic!
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From: Corona Del Mar, CA
2019 SL450, 2019 E450 Luxury Trim Wagon, 2024 BMW I7 xDrive60
Wondering where you are with this issue? My dealership just got back to me and expected response, "cannot duplicate action" and "refer to user manual for reasons system may activate". Svc manager told me to call their Customer Service CAC to file complaint which I did. 1-800-367-6372
Not sure what happens next.
Not sure what happens next.
Senior Member
Joined: May 2008
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From: USA
2018 S63, lowered
Stream - my 2019 E300 just did this on a trip between NC and NY. Applied the brakes at about 70mph as I was changing lanes on I-81 in MD. I believe it "saw" the truck in the right lane and braked hard because it thought I was going to hit it. (I was changing from left to center lane...)
I had to step on the gas and override it so that I did not get creamed by traffic behind me. It felt like about a 40% brake application - so not as hard as yours, but a big surprise to me and an unwelcome one at that.
No issues since then and I am steering a bit further away from anything as I make lane changes with Distronic on. I chalked it up to tech that is helpful, but imperfect, but like you, I sure didn't appreciate it.
I had to step on the gas and override it so that I did not get creamed by traffic behind me. It felt like about a 40% brake application - so not as hard as yours, but a big surprise to me and an unwelcome one at that.
No issues since then and I am steering a bit further away from anything as I make lane changes with Distronic on. I chalked it up to tech that is helpful, but imperfect, but like you, I sure didn't appreciate it.
That's EXACTLY what my 2018 S63 has done to me twice. Once was at highway speed and once in a 45mph zone. It's extremely unsafe. I've told anyone that will listen to me that the system that's supposed to "assist" me in the case of an actual accident is ultimately going to CAUSE an accident.
It's violent/abrupt when it happens and if you don't either mash the go pedal as fast as you can, or swerve back into your lane, you're going to get rear-ended- and for any eye witness it would "appear" that you could have done it intentionally! They'd see you change lanes and then for no reason what so ever jam your brakes on. It's a serious hazard and I cannot believe that MB has this in place as a "safety feature".
I THINK you can actually turn the function off, but then every time you key cycle the car it defaults back to "on". Can anyone confirm this? Is there a way to turn it off, completely?
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That's EXACTLY what my 2018 S63 has done to me twice. Once was at highway speed and once in a 45mph zone. It's extremely unsafe. I've told anyone that will listen to me that the system that's supposed to "assist" me in the case of an actual accident is ultimately going to CAUSE an accident.
It's violent/abrupt when it happens and if you don't either mash the go pedal as fast as you can, or swerve back into your lane, you're going to get rear-ended- and for any eye witness it would "appear" that you could have done it intentionally! They'd see you change lanes and then for no reason what so ever jam your brakes on. It's a serious hazard and I cannot believe that MB has this in place as a "safety feature".
I THINK you can actually turn the function off, but then every time you key cycle the car it defaults back to "on". Can anyone confirm this? Is there a way to turn it off, completely?
It's violent/abrupt when it happens and if you don't either mash the go pedal as fast as you can, or swerve back into your lane, you're going to get rear-ended- and for any eye witness it would "appear" that you could have done it intentionally! They'd see you change lanes and then for no reason what so ever jam your brakes on. It's a serious hazard and I cannot believe that MB has this in place as a "safety feature".
I THINK you can actually turn the function off, but then every time you key cycle the car it defaults back to "on". Can anyone confirm this? Is there a way to turn it off, completely?
Last edited by W205C43PFL; Sep 9, 2021 at 06:33 PM.
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Senior Member
Joined: May 2008
Posts: 445
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From: USA
2018 S63, lowered
Wait, so are you saying that when you set it to Early, Medium, Late or Off in Vehicle > Assistance > Active Brake Assist it sets it back to On after you restart the car? Sounds like we need another ODB module then to keep the setting persistent (after the eco start/stop disable module). I guess also turn off Lane Keep Assist so it doesn't brake on certain lane markings.
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Not quite sure why they set it to that to be honest, I guess because it is a "safety feature" and MB wants the driver and passengers "protected" incase they forgot to turn it back on, even though it is proven to be accident inducing at times.
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2024 S580
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Newbie
Joined: Sep 2021
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2021 GLA250
new 2021 GLA sudden braking
I've had my 2021 GLA for less than 2k miles; it's already been in the shop for two weeks after which I was told they either couldn't replicate my problems or the systems were functioning as designed.
Last night I was in light suburban traffic, at least 50 feet from the car ahead, and the brakes slammed on for an instant. Very scary; lucky no one was tailgating me. I see that this problem has been described in this form many times, dating back more than a decade. Do anybody know what's happening? Has MB acknowledged it in any way? Should it go back into the shop? Any info would be appreciated.
Last night I was in light suburban traffic, at least 50 feet from the car ahead, and the brakes slammed on for an instant. Very scary; lucky no one was tailgating me. I see that this problem has been described in this form many times, dating back more than a decade. Do anybody know what's happening? Has MB acknowledged it in any way? Should it go back into the shop? Any info would be appreciated.
Newbie
Joined: Jul 2021
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Gls450
My suggestion is to file a complaint with the NTHSA. Maybe if enough people complain they will open a case. Otherwise MB does not recognize this is a problem. I no longer own this car. We took a loss but I am not going to drive in fear of it spontaneously engaging again.
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I have a friend that had a S550 pre-facelift (forgot the year) here in Canada that got rear ended because of such malfunction, although I wasn't in the car, I don't see why he would lie to me as he likes Mercedes-Benz and had since moved on to a 2019 S560 4MATIC with zero issues. However, the driver at the rear was following too close I would believe which made the accident possible in the first place. Likely, he wasn't even injured. I also never heard of such an issue on the news from any car brands as well just like you so the technology has more benefits than drawbacks and I don't believe MB's active brake assist caused any death so far (at least I hope and not just not reported by the news). So I believe the malfunction was a one off. The most common so far is it (the system) giving people mini heart attacks when it malfunctions.
Last edited by W205C43PFL; Sep 11, 2021 at 08:39 PM.
MBWorld God!
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I am sure all of you love your cars despite these glitches now and there, no car is perfect after all. Don't be this guy (although for a different issue) : https://www.autoblog.com/2015/09/14/...des-s63-video/
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From: Maryland
2024 S580
I have a friend that had a S550 pre-facelift (forgot the year) here in Canada that got rear ended because of such malfunction, although I wasn't in the car, I don't see why he would lie to me as he likes Mercedes-Benz and had since moved on to a 2019 S560 4MATIC with zero issues. However, the driver at the rear was following too close I would believe which made the accident possible in the first place. Likely, he wasn't even injured. I also never heard of such an issue on the news from any car brands as well just like you so the technology has more benefits than drawbacks and I don't believe MB's active brake assist caused any death so far (at least I hope and not just not reported by the news). So I believe the malfunction was a one off. The most common so far is it (the system) giving people mini heart attacks when it malfunctions.
Do you know who they deemed at fault for that accident?
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Maybe the insurance company was able to pull data from both vehicles? I am not sure. What do you think?
Last edited by W205C43PFL; Sep 13, 2021 at 09:06 PM.
MBWorld Fanatic!
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From: Maryland
2024 S580
Typically the car in the rear is always at fault, because they should always be able to react to what the car in front does unless they are following too close, I was interested to hear if they would blame it on him since he had a vehicle malfunction.
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If they had done that, my friend could had provided proof that the brakes were checked at the dealership from last service (he has PPM) and that all recalls (especially safety ones) are addressed. Unless there is more to it, I don't quite know how the insurance works so that is just my assumption on what will happen.
Last edited by W205C43PFL; Sep 14, 2021 at 07:27 AM.
Newbie
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2021 GLA250
Either way, and thank goodness nobody was hurt, the fact remains that unexpected sudden braking was responsible and remains a known problem for this vehicle. It's possible that so few reports of injury are due to the fact that it happens so quickly and there's no record of it, making it difficult to report.
As for the justification that it has prevented many accidents, that's small comfort to those of us who have experienced it and now drive in constant fear of it happening again. As for the explanation of tailgating, suppose there had been no tailgating but the road conditions had been slick and icy? Likely to be the same outcome.
Yesterday I filed a complaint with the NHTSA. That, along with my call to the dealer, at least puts me on record as making the problem known to authorities. If it happens again and there are damages, that should bolster my claims.
As for the justification that it has prevented many accidents, that's small comfort to those of us who have experienced it and now drive in constant fear of it happening again. As for the explanation of tailgating, suppose there had been no tailgating but the road conditions had been slick and icy? Likely to be the same outcome.
Yesterday I filed a complaint with the NHTSA. That, along with my call to the dealer, at least puts me on record as making the problem known to authorities. If it happens again and there are damages, that should bolster my claims.
MBWorld Fanatic!
Joined: Jun 2015
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From: Maryland
2024 S580
Like I said, this is not a Mercedes thing. I experienced it in my Lexus and a Jeep Grand Cherokee.
MBWorld Fanatic!
Joined: Nov 2015
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From: Newcastle, WA
2019 S63 4Matic+, 2018 E400 Cabrio, wardens car.
I just purchased a 2019 S63 with 9000 miles on the clock and it behaved like this twice on the freeway last night. Going to take it to the dealer next week to see if they can check everything. Very scary to say the least.
Thread Starter
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From: Corona Del Mar, CA
2019 SL450, 2019 E450 Luxury Trim Wagon, 2024 BMW I7 xDrive60
Either way, and thank goodness nobody was hurt, the fact remains that unexpected sudden braking was responsible and remains a known problem for this vehicle. It's possible that so few reports of injury are due to the fact that it happens so quickly and there's no record of it, making it difficult to report.
As for the justification that it has prevented many accidents, that's small comfort to those of us who have experienced it and now drive in constant fear of it happening again. As for the explanation of tailgating, suppose there had been no tailgating but the road conditions had been slick and icy? Likely to be the same outcome.
Yesterday I filed a complaint with the NHTSA. That, along with my call to the dealer, at least puts me on record as making the problem known to authorities. If it happens again and there are damages, that should bolster my claims.
As for the justification that it has prevented many accidents, that's small comfort to those of us who have experienced it and now drive in constant fear of it happening again. As for the explanation of tailgating, suppose there had been no tailgating but the road conditions had been slick and icy? Likely to be the same outcome.
Yesterday I filed a complaint with the NHTSA. That, along with my call to the dealer, at least puts me on record as making the problem known to authorities. If it happens again and there are damages, that should bolster my claims.
MBWorld Fanatic!
Joined: Nov 2015
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From: Newcastle, WA
2019 S63 4Matic+, 2018 E400 Cabrio, wardens car.
I went to the MB Dealer in Bellevue, WA today and the SA basically told me it either works or it doesn't. He also suggested I turn it off in the city, when dark or when it is raining hard, which is basically all the time in the winter here. I am going to just turn all that crap off and only use it when I am out on the open road. If it happens again I am going to start logging it and if they cannot fix it I will look at next steps. Pretty amazing that they have a design flaw like this and no one has been hurt or injured with this Jekyll and Hyde feature set.
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From: Europe
223.168 & 213.012 & 906.633 & 214.005
I went to the MB Dealer in Bellevue, WA today and the SA basically told me it either works or it doesn't. He also suggested I turn it off in the city, when dark or when it is raining hard, which is basically all the time in the winter here. I am going to just turn all that crap off and only use it when I am out on the open road. If it happens again I am going to start logging it and if they cannot fix it I will look at next steps. Pretty amazing that they have a design flaw like this and no one has been hurt or injured with this Jekyll and Hyde feature set.
If the system has a design flaw, a bug, there is no way to claim it either works or it doesn't. Assuming the "it doesn't" means active brakes do not activate. Otherwise obvious, something either works or is broken and needs to be fixed.
Junior Member
Joined: May 2021
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From: NYC
18 s450 4matic
only had 1 experience with this malfunction. one late night I was making a right turn onto a street with trees lining both sides of the street on a four-lane street with street lamps also on both sides of the street and my car just emergency broke from 15mph to 0 with not a single car to be seen. On the next service, I told my service advisor about this and they came back with "could not duplicate issue". They did a software update and hasn't happened since (been 3months now).
MBWorld Fanatic!
Joined: Dec 2006
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From: Europe
223.168 & 213.012 & 906.633 & 214.005
only had 1 experience with this malfunction. one late night I was making a right turn onto a street with trees lining both sides of the street on a four-lane street with street lamps also on both sides of the street and my car just emergency broke from 15mph to 0 with not a single car to be seen. On the next service, I told my service advisor about this and they came back with "could not duplicate issue". They did a software update and hasn't happened since (been 3months now).
