Happy new year everyone,

My father owns new S500, his car is Nov/2020 production which is one of first cars delivered basically in the region here... he is facing 3 issues currently and I told service center about it in the first service visit but they didn't find any fault and they just updated software.
The first one is safety hazard for him and he said he is scared from driving the car now, rest are annoying and kinda sad to see in new car:

1. The car at low speeds all of a sudden brakes (no emergency brake warning or any traffic around or any beep sounds), it just does it randomly and my grandmother hit the back seat screen once with her head (didn't have seatbelt on sadly), my father and my sister both experienced this and said without seatbelt we will hit the front window, it does this randomly and everyone experienced this at traffic speeds basically (rear car barely missed them).

2. This was rare but happened like 4 times during first year of ownership, the car doesn't start at all and the battery system (48V) goes faulty, after 30-40 mins staying away from the car it starts normally with no indication of issues, the EQ Power/Charge indication showing normal functionality.

3. The handbrake sometimes seems jammed, the car doesn't move after putting it on gear (R/D) until you hit accelerator pretty hard and we get bang sound, then vehicle rolls and operates normally.

So would love to know if anyone experienced these issues on W223 specially the first one and if they had it fixed so at least I give an idea to my service center to diagnose, or if one of the assistant systems causing this (I don't think its emergency brake assist or active lane assist), today I turned off two by default enabled manoeuvring features I saw on parktronic menu which might be the cause of this (but I'm just guessing here).

Thanks.

I am sorry to hear about the issues but 48V battery system issues are common on the forums across multiple Mercedes models, unfortunately despite our hopes that they fixed it entirely on the W223, it ended up not being the case it seems.

The active brake assist may be impaired by dirt or salt and it does happen on other MB models too, I am sorry to hear that it happened for you, if you suspect the sensor itself is faulty you may get it checked by the dealership otherwise you may also disable it in the infotainment system if you don't wish to have it on.

The handbrake "being jammed" is common after the vehicle was sitting overnight if it was driven in the rain. That is normal.

The 1st one is, indeed, very dangerous. I am not sure if MB calls it 'Emergency Braking Assist' but I think it is called 'Active Brake Assist'. If it were me, I would definitely disable this feature under the 'Assistance' menu.
After the MB service centre updated the software, has it happened again? If no, then maybe it is a big software bug. If not, it is very troubling.
BTW, when you said 'low speed', what speed range is it?
By no traffic around, you meant no cars and people or anything within, say, 10-metre (or, 30 feet) in front of the car?

Yeah reading some other threads it seems it's an issue across the range a very strange one tbh since majority of Mercedes cars have 48V system.

I don't think what I mentioned is caused by active brake assist, the reason is in active brake assist it beeps when it goes active, but here there's no warning or beeping or any sort of sound, just sudden emergency stop which I doubt it's active brake assist, I suspected some sort of park assist thing but need more feedback to confirm it.

As for hand brake the car is cleaned daily (which was my intial thought as a cause) but so does all the other cars in the garage like G class, Porsches, BMW also W222 was parked on same garage and cleaned daily didn't have this issue at all, I suspect something else or new hand brake system that's more prone to water?

Anyway thanks for your feedback.

Again correct me if I'm wrong but don't active brake assist beeps when it goes active? I thought of disabling it but considering the speed my father and sister both mentioned + no warning at all displayed or sound, I thought it's either some other sensor or the 48V causing this for some reason since it have some faults.

As for software update done, I picked the car from service and changed the settings of active brake assist sensitivity to "late" for my father just to be sure, but 10 days later it happened again, I checked the settings still the same as I configured but now I disabled the parktronic manoeuvring ones.

My father and sister both said at traffic speed of around 10-30km/h it happened, for my sister it was during normal traffic but she wasn't very close to any object or a car around her (just normal distancing), for my father it happened with no traffic around last time, it happened for him so far 4 times now.

I am not sure if it beeps or gives any kind of warning when ABA kicks in to stop the car. Even if so, it would happen so fast and abrupt that you most likely would not be aware of it.
I experienced a few times when ABA stopped the car. It all happened so unexpectedly. Also, as the brakes were applied so fast, there was a very loud 'bang' noise (as if the car has hit something).
After the events, there was nothing on the 2 panels indicating what has happened. I went into the Message centre and no new message recorded.

I would expect when any kind of emergency assistance is triggered, the internal computer would have saved it in a log. Eg on 2021-12-01 15:23 at GPS xxxxxxx N xxxxxxx E, car at 15 km/h, front left sensor triggered algorithm 165 (ie, a nearly object is detected) and ABA kicked in. Something like that, you know what I mean. If so, the service centre can easily pinpoint what has happened.

no problem, happy to answer.

There are two systems but they do work together at times. Collison prevention assist includes forward collision warning and active brake assist. The former warns you of a possibility of collision, the active brake assist actually applies the brake at full threshold when you apply the brakes.

Nice fleet of vehicles : ) As for the handbrake, I am not sure, for example on my C-Class it does that sound you are describing after it being parked overnight when the components are wet.

Looks like best or nothing has not yet appeared on the W223 launch. Unfortunately.

The same company that sliced the ball into the woods on the V167 launch has duffed the tee shot again on the W223. Not sure if the ball made it to the ladies' tee...

Next up is the W206 launch. Maybe the third time will be the charm.

The bang noise could be the transmission struggling to shift the appropriate gear because of this sudden event the ABS system could had kicked in as well.
The event most likely is saved but not easily accessible, probably stored in the car's "blackbox"

Hopefully it does work out on the W206.

Instead of disabling it, you may also consider setting it from warn early to warn late or normal. For the active brake assist, you could also set it to brake early or brake late or normal.

Edit: Sorry about that, you already mentioned it.

Yes, I would think so of this ''blackbox''.
And an authorized MB dealer/service centre should be able to access this data, even if it is not allowed for the car owner to know what and why the car had made a certain action.

And, same as OP and as your suggestion, I have already set the Active Brake Assist to 'Late'. I hope this will vastly migitate the situation.

I had issue number 2. Had it towed to the dealership and they fixed something with a bad ground.

Issue number 3 happens on occasion. I'll put the car in gear and the parking brake doesn't disengage. I have to put in park then back in gear for it to move. This happened in my GT53 as well.

I have W206 in order coming soon for my wife, so it better works lol.

My wife will get heart attack if such a thing happened to her all of a sudden.

What I did now is I sent an email to Mercedes explaining this, they said it will take 5 days to investigate this issue and they will get back to me, they will work with dealer also to get last service record and see what is happening here, so hopefully it works out, if they call I will ask them regarding blackbox thing if they can get data from it.

Yeah I guess if it happens again I will call roadside assist to have it towed, I will also try your method of parking brake and see if it works, Thanks.

Good! If you have any progress or news of this 'sudden braking' issue, please post here to keep the community up-to-date.
TIA.

Will do for sure, Thanks.

Hopefully, keep us posted.

Yes hopefully, congrats on your W206, looking forward to hearing what you think of it and pictures of the vehicle when you receive it.

Thanks will do, not sure if more delays expected but last update I got is 3 months from now and sadly Brumester system was removed.

As for S class, the dealer picked the car from home just now and they gonna do full inspection about these issues they said, if they found an issue a replacement car will be sent until investigation is done.

Sorry to hear about an option being removed.

As for the S class, wow that is so nice of your dealership to do that, first time I am hearing such a thing especially them coming to pick it up from you and on top of that, offering to replace the car with no questions asked. That is refreshing to hear. I am used to hearing MB dealerships telling the car owners to tow it to their dealership and wait a few business days for them to do a diagnostic with absolutely no loaner. I am also used to hearing MBUSA buying back vehicles after repair for the same issue for 30 days as part of the lemon law, otherwise they would just repair the vehicle and give it back to you. For the dealership to do both of the things I mentioned earlier, it must mean you are a V..VIP to them and they need to do anything it takes to keep you as a customer.

Either way, I hope it all works out for you for both cars.

​​​​​​My father was buying every generation of S class since 80s with W126, he didn't skip a single generation so they should treat him properly tbh lol, since all of these cars on this same dealer, we like the dealer they truly appreciate loyal customers, hence despite issues my father still loves and trust the car, he is old school style of driving yet he told me don't turn off all the systems, it's gonna do more good than bad, but currently it's scaring him.

A replacement car will only be given in this dealer if a car have a fault, if no fault found they just gonna send it back to us basically.

Ah that makes sense!

For the replacement car, I wonder if they are able to give you a car that is identical or close to the spec you have, fingers crossed.

It depends what they have available, like 2019 G500 once had some issues and they gave us choice of A35 or E class as a replacement until it's fixed, sometimes you have to wait several days, but never got S class for replacement tbh, it's very rare we have issues with the car anyway.

Love the golf analogy...I get it! It is however the most advanced and sophisticated driver and golf ball on the planet.

They are cramming so much tech so quickly that these issues are impossible to avoid, so much overkill.