sjd_boston

Has anyone had an issue with Pre-Sense Plus braking very hard when passing other cars taking a right of left hand turn in front of you? My A8l 4.0 has slamed the brake on if the vehicle in front of me slows to turn and I try to drive by on the right or left. Both times it was around 35 mph and i had plenty of clearance to get around. In the first case the car behind me just honked. In the second case they locked up and missed rear ending me by inches. I stopped to apologies to the second person (he was in a jeep with roof and doors removed) and he said he had no clue why my car would have stopped. The car turning was actually in a left hand turn lane and i was in a lane to go straight.

MP4.2+6.0

Answer may be sort of in your post ===> "and i had plenty of clearance to get around." Car doesn't make judgments about ad hoc work arounds. If it sees something in apparent vehicle path it will intervene at some point. Can also come up in odd curved situations where you are actually in a distinct lane from another vehicle, but some steering input will be required for the lanes or curves involved. It is coming up with autonomous more generally too. I recently came upon a Cruze autonomous ride stopped dead in its tracks In SF backing up traffic for blocks simply because it had no idea how to slightly swerve around another car turning in front of it that got stopped in is own tracks in a clogged intersection. Really reminded me these things are not ready for prime time in anything other than pre programmed scenarios, more than a few of which they seem not to have fully thought through.

FWIW, my practical solution if I come across something dubious or start to get the more urgent chime warning is to cover the brake very lightly. Once it knows you are attentive to the situation via a little brake pedal feedback it generally lets you manage rather than proceeding to full on intervention. Yet more subtle: be aware of it too for other vehicles that will increasingly have systems like these too. In other words, also avoid the situation the driver behind you who barely missed your car was in where he/she "assumed" some things that may not apply with auto safety system nannies in cars in front or otherwise around you.

jahummel

I just had that happen to me the other day, with the car in front of me turning right. It was an extremely hard braking jolt right after I got the visual and aural warnings. I just chalked it up to my rate of closure on the slowing vehicle in front of me. +1 to what MP said about covering the brake pedal.

lauwersp

The other thing I would add to MP4.2+6.0's answer is that YOU know that by the time you actually reach the vehicle it's concerned about it's likely completely out of the way by then. If something stops it, you'll take evasive maneuvers. The problem is, that relies on the S8 knowing you're actually paying attention which for the most part, it can't. Let's say you think it'll be out of the way and you're not paying attention... They stop before they're clear... you're not expecting it and paying enough attention... your S8 hits them. The first question I think you'd have in that situation is "What happened to the Pre-Sense Plus braking?!?"

I DO also agree that if the S8 see's you're interacting in any way with the braking system, it's more apt to think you're aware.

LexusLSguy

Could also be alignment of the sensors. In my experience, although with the Subaru Eyesight system, after a windshield replacement the system had to be realigned. It was triggering too sensitive outside my lane. If it is too sensitive I recommend a dealer take a look.

lauwersp

@LexusLSguy – You are completely right. Sensor alignment is an important issue... especially if you have repairs made that "touch" sensors.... but sensors have lots of reasons why they lose their alignment. I will say that in the case of MY S8, I feel like my sensors are aligned and as far as this feature being talked about, my S8 exhibits this behavior, but I honestly feel like it's operating as intended. In every case where this happens to me (which is not often), I would fully admit that I WOULD have hit the car being warning about IF that car were to stop at the point that the Pre-Sense Plus Braking gets invoked AND I weren't to take evasive maneuvers. It's hard to remember that no matter how sophisticated the sensor arrays in ALL the modern cars, they can't take into account what's going on in your head.

Passing a car when the adaptive cruise control has already slowed you down is another great example. When I'm in control, and I change lanes to pass someone on the freeway, I begin accelerating long before I've completely entered that lane I'm moving into. Mercedes next generation system will actually look into that lane to see if there's adequate room to accelerate while maintaining your gap (just in case you're changing lanes but that lane is no faster than the lane you're in), but also remember that it has to still keep other possibilities in mind, like what if you change your mind midway through lane changing. YOU know you're not changing your mind, especially because you are accelerating, but these new partially autonomous or assisted driving features have to be trained for generally every possibility. Not everyone is as good at driving (and being intelligent) than everyone in this group.

Mike911A8

Brake guard can be disabled by going to Sport mode stability control. Can't access ACC in Sport stability mode.

ehalbre

We have a 2023 etron Chronos edition bought in December and the hard automatic brake has happened three times. Twice to me and once to my husband. All during left hand turns with no cars in front of us. This last time which was last week I was turning onto our street with a car behind me and nobody in front of me or coming toward me from the front and the car hard braked by itself and the car behind me almost slammed into me. It's incredibly dangerous and I'm just glad the car didn't hit us. We have had numerous problems with this car and the sensors and have had to have it in for service 5 times. It is currently at the dealership awaiting an answer from Germany. I don't ever want to drive this car again as I feel it's going to cause an accident and injure us or others.
I honestly hate all the pre sense nonsense on this car. I know how to drive a damn car, I don't need it telling me what to do!

A8L_New_England

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Wrong forum, necro-thread.
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