Distronic Plus help

[Andman99]

Hi All. I have a C300DE which has been a wonderful experience, mostly. The big problem I have is with Distronic Plus. Specifically when the car suddenly rapidly accelerates above the limit I have set. As an example, I set the limit to 50mph on a stretch of motorway with this reduced speed limit. At some random point, where there are no visible 70mph or national limit speed signs (played dashcam footage back), the car resets the limit and accelerates from 50 to 70mph. I am told by the dealer it is meant to do this. Surely not?! Any suggestions gratefully received.

 

[markjay]

Welcome.

First thought - was there any speed sign at all - e.g. on a parallel road etc? And, is the windscreen clean, especially the part in front of the rearview mirror?

Then, my other car (not MB) also receives speed limit info in real time via GSM (i.e. not just via the Roadsign Recognition Assist), including temporary speed limits on motorways, but I don't know if you car has this capability.

And last, did the dealer update the software for the driver aid systems to the latest version?

 

[Andman99]

Thank you for the welcome and response.

There were no speed limit signs visible leading up to the acceleration (as per dashcam footage). The stretch of motorway in question has a reduced limit of 50mph for several miles, which is why I set a limit of 50mph. My understanding of the Distronic Plus system is that it will decelerate and accelerate according to traffic conditions, but never accelerate above the limit I have set (unless I depress the accelerator). It just doesn't feel as safe accelerating to a limit above the one I had set.

 

[John N]

Hi All. I have a C300DE which has been a wonderful experience, mostly. The big problem I have is with Distronic Plus. Specifically when the car suddenly rapidly accelerates above the limit I have set. As an example, I set the limit to 50mph on a stretch of motorway with this reduced speed limit. At some random point, where there are no visible 70mph or national limit speed signs (played dashcam footage back), the car resets the limit and accelerates from 50 to 70mph. I am told by the dealer it is meant to do this. Surely not?! Any suggestions gratefully received.

What is active distance DISTRONIC Mercedes?

DISTRONIC: How does it work? The Active Distance Assist DISTRONIC is available in the Driving Assistance Package and makes driving easier by adjusting the distance to vehicles ahead. Within a speed range of 0 to 210 km/h, the intelligent assistance system brakes and accelerates automatically.

When driving in a q of traffic the car will always keep a Safe Distance between you and the Vehicle in Front. If you have Cruise Control set to the Roads Limit (70 MPH) and the Vehicle in front speeds up your car will Accelerate up the that Limit!

I am assuming that you are trying to set the Cruise Control to 50 MPH through the Reduced Speed Limit Area! If so it will stay locked into that Speed until you either Accelerate or Increase the Limit!

 

[Andman99]

Hi John

The C300de did come with the Driving Assistance Package. So, on the steering wheel, I use the centre toggle to set the speed limit to 50mph. I don't touch the other two toggles. The car will then accelerate (to 50mph) or brake as determined by traffic conditions. What I have been witnessing for the past 8 months is a random reset of the limit I have set from 50mph to 70mph. The dealer has told me this is normal behaviour, and the car must be picking up an errant 70mph speed sign. Dashcam footage show this not to be true. What I am trying to understand is why is this happening? Is this me not understanding how to use the system, or does the car have a problem, despite the dealer saying otherwise?

 

[markjay]

And last, did the dealer update the software for the driver aid systems to the latest version?

?

 

[Germgh0st]

As said it may be picking up the speed limit from another source, like GPS. Road signs aren't always available or easily red, hence GPS is used for backup.

 

[Londonscottish]

What is active distance DISTRONIC Mercedes?

DISTRONIC: How does it work? The Active Distance Assist DISTRONIC is available in the Driving Assistance Package and makes driving easier by adjusting the distance to vehicles ahead. Within a speed range of 0 to 210 km/h, the intelligent assistance system brakes and accelerates automatically.

When driving in a q of traffic the car will always keep a Safe Distance between you and the Vehicle in Front. If you have Cruise Control set to the Roads Limit (70 MPH) and the Vehicle in front speeds up your car will Accelerate up the that Limit!

I am assuming that you are trying to set the Cruise Control to 50 MPH through the Reduced Speed Limit Area! If so it will stay locked into that Speed until you either Accelerate or Increase the Limit!

Yeah, but that's Distronic, not Distronic Plus.

 

[Andman99]

?

I am told this is the case. In fact, it was after the last software update (circa 8-12 months ago) that this problem started. The car has just been serviced, so hopefully it's all up to date now (it's still at the dealership)

 

[st13phil]

Is there a cluster option to change the behaviour of Distronic Plus on the car? In particular, is there an option to "follow" speed limit changes (for example when you leave a built-up area and the posted limit changes from 30mph to NSL) automatically?

On both the cars I had with Distronic Plus (a 2012 and a 2015 E63) neither had that feature and would only ever accelerate up to the speed I'd preset, regardless of the speed limit, but maybe Mercedes have introduced it on later versions? What does the car's manual say on the matter?

Edited to add:

I've just found this explanation from Mercedes-Benz:

Easy Tech: DISTRONIC | Mercedes-Benz Group

"Einfach Technik" explains technologies and innovations around the Mercedes car. DISTRONIC gets things started: the Active Distance Assistant.

group.mercedes-benz.com

Does your car have "Active Speed Limit Assist"?

 

[st13phil]

...and more on Active Speed Limit Assist, including enabling / disabling it in this clip:

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[Andman99]

Is there a cluster option to change the behaviour of Distronic Plus on the car? In particular, is there an option to "follow" speed limit changes (for example when you leave a built-up area and the posted limit changes from 30mph to NSL) automatically?

On both the cars I had with Distronic Plus (a 2012 and a 2015 E63) neither had that feature and would only ever accelerate up to the speed I'd preset, regardless of the speed limit, but maybe Mercedes have introduced it on later versions? What does the car's manual say on the matter?

When I bought this C300de (new) in 2020, just pre-covid, nothing like this was explained. It was simply "set your limit, and the car will do the rest." The car is currently at the dealership, so I can't check the cluster settings yet.

I am aware of media reports of other cars (e.g. BMW) experiencing similar things, where the car accelerates beyond the set limit (up to 100mph in some reports), or suddenly brakes (from 60mph to 30mph in some reports). Some owners have been refunded the cost of the adaptive cruise control package, but the elephant in the room is that not one company has addressed the issue.

 

[Andman99]

...and more on Active Speed Limit Assist, including enabling / disabling it in this clip:

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Exactly - "the maximum speed being the stored speed." I assume the "stored speed" is the speed I initially set.

 

[markjay]

I am told this is the case. In fact, it was after the last software update (circa 8-12 months ago) that this problem started. The car has just been serviced, so hopefully it's all up to date now (it's still at the dealership)

OK, but keep in mind that MB dealers do not update software as a matter of course during a service - they will only update the software if there's a specific customer complaint.

Also, to clarify, I am referring to the instrument cluster and driver aids software aka 'firmware', not simply to the maps data on the navigation system.

 

[Andman99]

OK, but keep in mind that MB dealers do not update software as a matter of course during a service - they will only update the software if there's a specific customer complaint.

Also, to clarify, I am referring to the instrument cluster and driver aids software aka 'firmware', not simply to the maps data on the navigation system.

Thanks - yes I understand re: menu cluster. I'll mention the update when I pick the car up on Friday. The car is only just 3 years old, so I trust (more fool me) that the correct procedures have been followed.

 

[markjay]

Thanks - yes I understand re: menu cluster. I'll mention the update when I pick the car up on Friday. The car is only just 3 years old, so I trust (more fool me) that the correct procedures have been followed.

Updating software is time-consuming, and requires the use of STAR (the dealer will have a limited number of STAR units and and a limited number of STAR-qualified technicians), and so they will follow the rule of 'if it's not broken, don't fix it' - they will only apply a software update is there's a specific customer complaint, or if there's an official recall.

 

[Andman99]

Updating software is time-consuming, and requires the use of STAR (the dealer will have a limited number of STAR units and and a limited number of STAR-qualified technicians), and so they will follow the rule of 'if it's not broken, don't fix it' - they will only apply a software update is there's a specific customer complaint, or if there's an official recall.

Ok. Thanks. This is good to know and I'll enquire when I go and pick it up.

 

[st13phil]

I’ll repeat my two questions:

1. Does your car have "Active Speed Limit Assist"?

2. What does the car's manual say on the matter?

 

[Andman99]

I’ll repeat my two questions:

1. Does your car have "Active Speed Limit Assist"?

2. What does the car's manual say on the matter?

Well, it would have been nice to have all of this explained when I bought the car. It's a C300DE AMG Line Night Edition Premium Plus. I was told it came with the Driving Assistance Package, which includes Distronic Plus. This was explained to me as a sophisticated cruise control which will brake and acclerate (to your set speed limit, not the road's limit), according to traffic conditions.

The car isn't with me, so I can't check re: Active Speed Limit Assist or manual However, when I'm in control of the car and approaching roundabouts, or junctions, or when the car enters a reduced speed zone, it will brake when I take my foot off the accelerator. But I find it only does this effectively in Economy mode; in Comfort mode, it's less effective and more of a gradual braking.

 

[Ted]

I found the speed limiter more useful than cruise control in temporary speed limit areas.
Does your car have this?