I had a startling and scary experience in my 2017 300 E today. I was driving about 35 mph on a major street with no traffic anywhere nearby. Suddenly, the brakes slammed on hard and the seatbelts retracted very quickly. I did not initiate any of this and, as I said, there was no traffic to be seen. At first, it felt like we hit something but there was nothing to hit and no damage to the car. The car seemed to think a collision was imminent, but it wasn’t. Could have been dangerous if someone was behind me or if I had lost control in reacting to what happened. Has anyone experienced this and does anyone have an explanation of what happened and whether there’s a way to prevent it from happening again?

 

Yes this has happened to me maybe three times in ownership. It has happened twice on the same street for me. I think there is a road sign that is in the center island that reflects the radar. Unfortunately no way to reduce the occurrence, it’s just part of having this technology

 

I experienced this three times, all while I was in complete control (not with cruise control), miles clear of anything ahead of the vehicle, with nothing showing up on the assistance screen in the cockpit (which will indicate if there's something ahead detected by the radar).

It doesn't seem to be radar or autonomous emergency braking related, as in my case I have since solved this by deactivating the adaptive steering assist system, which was on, but not even ACTIVE during these incidents. By turning off the system I mean using the button with the steering wheel on it, make sure it is OFF (blank, not red). The button is located next to the steering column, among the row of buttons that include switches for HUD, parking sensors etc. (This system only controls the steering bit of the autonomous driving, you would still have distronic and AEB.)

It's cool to have a function that has the car steering itself with reasonable competence, but so totally not worth the distinct chance of being rear ended and run over by a lorry.

This fix is probably not universally applicable, but I hope this helps.

 

I had a 2017 C43 with distronic which I drove 40K miles and I never once had an issue with hard auto braking.
I haven't experienced anything like it in the E either but I haven't driven it nearly as much.

There are some people on the forum that have reported a similar sudden braking as you have described.
Here's a similar scenario on the previous gen E class (w212): https://mbworld.org/forums/e-class-w...n-braking.html
And here's a thread where somebody is trying to gather members who have experienced a similar issue: https://mbworld.org/forums/mercedes-...functions.html

Tesla forums have people talking about it too: https://forums.tesla.com/forum/forum...king-autopilot

I know these false alarms can happen but I think the pros outweigh the cons (for me at least). These sudden braking situations can be scary and I would advise you visit your dealer to at least report the incident and have them pull data from the car.

Threads like this make me want to install a dashcam so I have video proof at least.

 

Thank goodness I don`t have these systems, I have been driving for 60 years and haven`t hit anything in all that time, these systems are not required and can obviously become extremely dangerous especially at high speed, I never ever want the sort of surprise mentioned here.
The only auto systems on my Merc are auto gearbox, auto high beam and auto stop/start with brake regeneration. I switched off auto high beam and disabled auto stop/start and brake regeneration shortly after purchasing the car, simple is best and you get less problems as the car ages and simple is easier to detect. These modern complex cars will be scrapped early, not because they are worn out but because the complex electronics are to expensive to fix.

 

I just happened to notice this thread. The exact same thing happened to me in my 2018 S560 sedan. Driving along, no cars anywhere, then WHAM! I thought maybe a bird flew right in front of the sensor or something. Anyway, it was a bit freaky, but I will not own another vehicle without a version of MB’s truly fabulous Driver’s Assistance Pkg. I’m an older guy and I know my reflexes are not what they were when I was in my 30’s or 40’s. I truly appreciate and highly value these accident avoidance systems.

 

I too would never own another vehicle without some kind of autonomous function. The benefits still out way the minor annoyance of this happening. I have had collision assist prevent one or two accidents for me already.

 

Me too!

 

I have not experienced the unexpected emergency braking, but I like having the automatic braking feature nonetheless. I am sure there is an explanation for what happened. I know that I find it disconcerting when on a freeway the system picks up a low speed limit sign such as one on an off ramp and the car abruptly slows, but that is nothing compared to an emergency stop.

For humans to catch up with the technology is a true challenge.

 

You can switch that feature off. I found that particular feature to be annoying as well. Can't remember just how it was turned off, but you can do it.

 

I find best off turning off the speed limit adoption, perhaps thats what happened with the OP. I've really never had an emergency stop for on reason and thats after a lot of miles on the 213 platform. 14.5 K miles on my 2018 E63 Wagon, 23K miles on my E450 Wagon and 10K miles on my E450 Cabriolet. So nearly 48K miles and it's never happened. One feature I do really like is the limit feature where the car will loose throttle response when you are right up close to something like the side of the garage door opening or bank ATM drive through or if you come really close the car will just abruptly apply the brakes.

 

Yes it is in the COMAND navigation, driver assistance -> speed limit assist. I keep it on even with that issue of catching off ramp speed limits, but I remember when it happens since my route is the same most days, and just double tap the accelerator pedal and it resumes back to the previously set speed.

 

To me thats a dangerous feature as you could have your mind on something else and the car quickly slows and you get rear ended. But what streamliner was talking about was the emergency braking feature and yes that can be turned off in the Assist menu. I leave mine on as I've never had it come on unexpected and have it come on when it should such as someone jamming on their brakes in front of me and ended up saving me from a collision.

 

I know we are talking about the collision braking assist as the main topic, but Streamliner and Hundens brought up the speed limit assist which automatically adjusts distronic cruise speed to the posted speed limit, but often catches off ramp signs. I was just saying they could double tap the accelerator pedal to keep the set speed.

 

Turned the auto speed limiter off, since it can be very annoying (and dangerous) when suddenly on the highway you drive 130 km/h (legal vMax here) and then suddenly it goes back to 70 km/h because it thinks there is a new speed sign............which there is NOT! Seems interesting to see what happens when people start driving around with fake speed signs of 30 km/h in the back of the car and show these when some car is coming too close to you from the back..............

BTW, you can easily set the auto speed limiter on for a specific situation by double pressing the "RES" (RESUME) button on the cruise control part of the steering wheel. The default then stays OFF however!

 

I disabled the speed assist because it doesn't understand "effective hours" or "school days" on signs. The auto braking function kicked in unexpectedly with maximum braking that reduced my speed from 45 mph to 15 mph in an inactive school zone. The following car nudged me slightly, luckily there was no damage.

 

Agree, it is too tricky to leave it on auto all the time.

(corrected my post before: you can double press the RES(UME) button on the steering wheel to temporarerly activate the auto speed limiter!)

 

Sorry, didn't mean to side track the discussion. I thought the two features were close enough in operation that it would be useful to discuss them together.

 

10 days ago I was driving in peak hour traffic in an inner city suburb of Adelaide when suddenly the emergency brake assist activated and the car slammed to a stop. An image of the car came up with a large red triangle from the left rear of the vehicle. There were no vehicles close to that part of the car. And, if there had been, why would my car bring itself to a stop as that would ensure that the car (should one have been there) would hit me from behind. I was pretty rattled by this. When I asked a staff member at MB he said that many things can activate the emergency assist e.g. an illegal radio jammer. OK, I might be able to accept that. However, a few minutes later a car stopped abruptly in front of me and I slammed on the brakes but hit the car anyway. No emergency brake assist activated at \that point. The MB rep had no explanation for this. Has anyone heard of something like this happening before?

 

This is a very old thread, so before responding, I scrolled back to see if I had responded before, and I had—back in 2019, when my 2018 S560 did it.. Fast forward to last year and my fairly new, 2022 S580 did something similar, TWICE, within a few months time.

I was driving down a multi-lane highway. In both instances, there were no other vehicles anywhere near me. Both days were clear & sunny, not windy. I was looking straight ahead and nothing crossed my path. In both instances, I was going maybe 35 to 40mph. The car slammed on the brakes, lights flashed, the seat belt cinched tightly and the car came to an abrupt stop. Had someone been on my tail, they would have most likely hit me. The dealer said “no code,” so there was nothing for them to fix.

My 2018 never repeated the event and my current S580 has not done it since those two incidents. That said, the S580 has been a nightmare and MB is buying the car back now.

Anyone experiencing these events, should contact MBUSA and inform them. Then, one day, when one of these incidents happens and someone is badly injured, they won’t be able to say they didn’t know of the problems.

 

Or the Australian equivalent to MBUSA... MBAUS?

 

Safety systems are great when they work. Auto braking system should really have a dual sensor verification system since it could cause a serious accident. Modern day Mercedes designers, which are the Mercedes accountants, determined it cost too much and showing a profit is more important.

 

My brother in his Tesla Y, had 2 instances of the car slamming on its brakes, when there was absolutely nobody ahead of or behind him…..while merging onto interstates. Very scary. Thankfully, there was nobody behind him when both of the above braking incidents took place, else he would have been rear-ended. Never experienced that in my 2022 E450.

 

Regarding the second part of your question as to why you rear ended the car in front of you, it may be because you had already stepped on the brakes, which might have deactivated the emergency brake assist feature. If you had been distracted and not paying attention then I think the car would have activated the emergency brake assist and prevented you from hitting the car.

I think the system is setup that if the driver is stepping on the brake pedal then the emergency brake assist is deactivated.

I am not 100% sure on that. It's just a thought.

I remember almost 10 years ago when I was driving my 2010 BMW 5-series RWD on the highway with slushy snow on the roads. I attempted to change lanes from the far left lane into the middle lane and the car lost traction. I was seconds away from driving head-on into the right side wall/barrier. I had the steering wheel correctly turned all the way to the left to try and save the car and I had my foot slammed on the brake pedal, but the car wasn't responding. Then for some reason I decided to take my foot off the brake pedal and the car instantly activated the Dynamic Stability Control system and corrected the spin and saved me from crashing into the side barrier. I had no idea DSC only activated if your foot is off the brake pedal.

 

My W212 (2014 E350) sensors/computers worked better than my W213 (2021 E350) do, both in Distronix mode and not. The blind spot reached further ahead and back. Also, I get an ear piercing beep at random times which never happened with my W212.