On p. 185 to the manual for my 2023 GLC 43, it describes braking assist for models without Driver Assistance Package as follows:

AUTONOMOUS BRAKING FUNCTION
From a speed of 4mph, the autonomous braking function may intervene in the following situations:
- at speeds up to 124 mph when approaching vehicles ahead
- at speeds up to 31 mph when approaching stationary vehicles

SITUATION DEPENDENT BRAKING ASSISTANCE
The situation dependent braking assistance can intervene from a speed of 4 mph in the following situations:
- at speeds up to 155 mph when approaching vehicles ahead
- at speeds up to 50 mph when approaching stationary vehicles

What is the difference between Autonomous Braking Function and Situation Dependent Braking Assistance?

Honestly, 31 mph not very fast, so this function seems fairly limited, at least if you don't get DAP. The thresholds for models with Driver Assistance Package are higher....155 mph and 62 mph for Autonomous and 155 mph and 62 mph for Situation Dependent. Really quite disappointing that Mercedes would go out of their way to purposely limit the safety of such a critical feature on models that don't have DAP. The casual car buyer is unlikely to fully comprehend the consequences of their decision to get or not get DAP until after they make the purchase and read the manual.

I wonder what BMW or Audi's thresholds are....would love to know.

 

There seem to be different versions of the owner's manual. You can find the updated manuals based on the manufacturing date of your vehicle online: https://www.mbusa.com/en/owners/manu...4-03-x254-mbux. The speeds are different from what you are posting. In later versions the situation-dependent assistance is also described more clearly. It's actually situation-dependent brake force boosting. So depending on the situation it boosts the brake force, whereas the autonomous braking assistant attempts to actually bring the car to a full stop. They are somewhat overlapping I suppose, but the autonomous braking assistance attempts to compensate for the driver's reaction time by applying the brakes quicker than the driver can, whereas the situation-dependent brake assistance ensures that the driver applies enough brake force and engages ABS. Most people do not apply enough brake force in an emergency. Many have never felt ABS, so they get scared when ABS kicks in and ease off the brake pedal. So to help these folks not crash, the system boosts the brake force on their behalf depending on the situation. One of the things they teach at driving schools is to properly slam on the brakes in an emergency and take full advantage of ABS. I highly recommend this. It lets you experience how the car feels and behaves in such a situation. After all as they say, practice makes perfect.

As for the thresholds being different between w/ DAS vs w/o DAS that has to do with the number of sensors. DAS adds additional sensors such as a stereo camera behind the windshield where w/o DAS it's only a single camera. More sensors make these systems more capable. I agree, many people don't know this and think DAS is only about DISTRONIC and such, but I've pointed this out before, DAS also makes the safety systems better.

 

OK, well that makes a lot more sense. I understand now. Thanks for your comprehensive reply.

My car is a 2023 GLC 43 coupe that was made in January 2023. The most recent owners manual that predates January 2023 is the version for June 2022. The next version after that that was June 2023, which I assume would not apply to me as it is six months after my car was manufactured. Further, that later revision shows the the car as having the big center screen (I have the small center screen) so the later one couldn't apply to me. In double checking the June 2022 manual, the thresholds for MPH for cars without DAP that I cited above appear correct. Can I ask why you believe those thresholds listed are incorrect? That would be very helpful to know.

 

I was looking at the GLC SUV. The speeds for the Automatic braking assist are higher for example 50 mph for stationary vehicles. Looks like there are differences between the Coupe and SUV strangely.

Page 213: https://www.mbusa.com/css-oom/assets...s-manual-1.pdf

 

OK, makes sense. One more thing on this feature. On page 184 of the 6/22 manual for coupes, it says that the Distance Warning Function for vehicles w/o DAP can aid in the following situations with an intermittent warning tone and a warning lamp: 1) at speeds up to 155 mph when approaching vehicles ahead and 2) at speeds up to 50 mph when approaching stationary vehicles.

I've purposefully tried tailgating a couple of drivers to test the function, and I get no warnings despite being way too close. Is there something on this feature I'm missing?

 

I turn Active Brake Assist OFF as soon as I get in the car. It's way too aggressive IMO and does not allow for flying up behind someone planning to cut over. When I get it tuned, I'm going to see if they can set the car to start with this feature off.

 

So I seem to have figured out what's going on. The "Brake Assistance" submenu is greyed out and so I can't modify the settings. What's interesting is that when I start the engine that submenu lights up and is then editable. But then returns to becoming greyed out again within seconds. Anybody know what this behavior is about?

 

If brake assistance is greyed out, that typically means the system is malfunctioning. Your observed behavior would indicate that it's trying to initialize it, but something isn't working, so it's greying it out. Interesting that you don't get a warning. Normally, there's a warning coming up as well if there's a malfunction saying brake assist is not available or limited.

 

OK, so I guess I need to go to the dealer for that.

There is one more thing that I've come across that is concerning to me. When I accelerate from a stop, the car surges in speed right before shifting into second gear. If I try real hard and go super slow, it is more manageable. But nobody drives like that, at least I can't. It is also more manageable but still irksome when I'm in Sport or Sport +. It is not present at all when using paddle shifters. It is worst in Comfort mode with automatic. Do you know what is at play here? Are there workarounds? Is it a software issue? It is really putting a damper on my enthusiasm for the car. I really don't like having my head snap back everytime I accelerate from a stop.

 

If you search the forums, you'll find that the transmission in the 43 models is a common source of complaints. Some people have issues with it. Don't really know what the percentage is, because the thing with forums is that you only hear from those that have issues. These transmissions adapt over time based on one's driving style, but sometimes it seems the adaptation can go haywire and resulting in jerky shifts. The adaptations can be reset by a dealer, so you can start over teaching the transmission your driving style, or you can just keep driving as the adaptation is a continuous process.

I see your car is a 2023. Is this car new to you? Was it preowned or was it a leftover '23 model that sat around for a long time? The reason I'm asking is because issues with the driving assistance and safety systems are frequently caused by low voltage issues. So if the car's been sitting around for a long time, the battery may have gone bad. Electrical issues can cause all kinds of funky behaviors. I've got some electrical gremlins in my '19 C63S Coupe that started after 5 years of ownership out of the blue, and I suspect my battery needs to be replaced.

 

I purchased the car Certified Pre-Owned with 6,500 miles on it from a MB dealer in New Jersey and had the car shipped out to San Francisco. I've only been driving it for about a week. I'm dropping off the car tomorrow at the MB dealership to get the Brake Assist looked at. Any advice that you can give on how I should couch the surging issue or advice I can give him?

 

Not a good omen if the previous owner kept it for only a year or less and driving it only for 6500 miles. Best advise I can give you is to ask the service advisor if you can go for a test drive with the foreman, so you can demonstrate the issue to them.

 

I figured out what is was. When you take your seat belt off, Brake Assistance becomes inoperative.

 

Ah, that makes sense. Didn't even think about that. It actually works in conjunction with the seatbelts. They tighten to strap you in when the automatic braking engages. So makes sense that the system is disabled if you don't wear the seatbelts.

 

Thanks for your advice on taking the service guy for a ride to demonstration.

 

So now that I've got the brake assist function working (now wearing my seat belt), I'm not getting any warning about following too close to vehicles ahead of me. On page 184 of the 6/22 manual for coupes, it says that the Distance Warning Function for vehicles w/o DAP can aid in the following situations with an intermittent warning tone and a warning lamp 1) at speeds up to 155 mph when approaching vehicles ahead and 2) at speeds up to 50 mph when approaching stationary vehicles. I cannot get this function to warn me no matter how close I tailgate someone. The function is dialed into "Sensitive" which should provide more warnings than any other setting. But I haven't received any warnings at all. I've read that some people on the forum shut this function off due to constant warnings. I'm not hearing or seeing anything. What is the experience of others on this forum?

 

I have the full driver assistance features and I don't recall ever getting a warning, but I also don't ride up on the cars ahead like that. I don't know how close you have to be tailgating for it to warn. Keep your distance and you'll be fine.

 

I don't normally follow that closely either...just testing the system. And it doesn't seem like the Distance Warning function does much.