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Old 08-23-2021, 11:16 AM   #1
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2019+ Sprinter Cruise Control Design Flaw

For those owners of Sprinter-based motorhomes, built on 2019 and later chassis, you should be aware of a major design flaw in the implementation of their adaptive cruise control.

If you drive for an extended period on cruise control on a road with light traffic, and the system doesn't see a vehicle in range of the radar in the front, after an undocumented extended period, the system will decide the system has failed, and will disable adaptive cruise control. This also disables active brake assist (emergency braking if an object is detected ahead).

When the adaptive cruise control is deactivated, you won't have any cruise control available - only manual driving using the accelerator pedal. The system will not fall back to standard cruise control (which doesn't use the sensors to maintain spacing).

Once the system is deactivated, it will not reactivate until the sensors are able to see a vehicle in front and you drive behind that vehicle for an unknown time while the sensors go through another calibration phase.

Our local Sprinter service has had our 2021 View several times, and recalibrated the sensors. On a June road trip, we lost cruise control for 5 days while driving in east New Mexico and west Texas. On our most recent road trip, we lost cruise control over 3 days while driving to/from Yellowstone National Park. In both cases, we were driving for an extended period without seeing any vehicles ahead. And the system only came back online when we were able to find a vehicle to drive behind until the cruise control reactivated.

According to Sprinter service, they checked with Mercedes engineering - and the system is operating as intended.

And, this would probably be OK for commercial Sprinter customers (the majority of Sprinter owners), when their Sprinter vehicles are driven almost entirely in urban areas which will always have other vehicles in front.

But for motorhomes travelling to state and national parks, especially off interstate highways, it is more likely there will be long periods without any vehicles in front of you.

I've tried to report this issue through Mercedes USA Customer Care - and their group (which is an outsourced phone support service) doesn't work for Mercedes, and doesn't have access to Mercedes corporate support or their engineering groups. And, Mercedes (in Germany) evidently won't talk with either customers owning Sprinter-based RVs or even Winnebago who builds a motorhome on the chassis.

So the likelihood of getting this design flaw fixed is very low.

What can you do about it.

First, if you have this problem, complain to your Sprinter service so Mercedes is hearing from their vehicle owners.

Second, if you are driving on a lightly travelled road under cruise control, every 30-60 minutes (period is unknown), try turning off cruise control briefly - and hopefully that will reset whatever timer the software is using to determine if there is a failure.

And, if you do lose cruise control, try to find a vehicle to drive behind for miles, until the system resets. Even if you have to slow down to increase the likelihood someone will pass you, who you can then follow, that may be better than running without cruise control or brake assist for hours or days...
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Old 09-04-2021, 11:40 PM   #2
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Hi Rprochnow,
When I read a story like this, it makes me glad that I own the 2019 Ford E-450. It is bone-stock simple, and its cruise control works the same way as my 1988 F-350 does. Could it be that Mercedes is trying too hard? Sometimes simpler really is better.
Is there and option to shut-off the adaptive control, and just have a simple cruise control?
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Old 09-05-2021, 04:10 AM   #3
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No option to fallback to normal cruise control. Plus you lose adaptive brake assist.

Appears MB engineering designed the software for urban commercial vehicles, not RVs...
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Old 09-05-2021, 07:52 AM   #4
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It does seem the new line is much like what we find on lots of electronics! They have ideas and the chips are there so they hang junk on as a sales item even if it makes driving worse!
We have a 2021 Honda Pilot with junk adaptive cruise control that does several nice things but in bad ways!
It has several settings for how far behind a vehicle we can get before it reduces throttle to avoid a collision! The problem is that the cruice control on lowest setting is a real problem when driving in moderate to light traffic like I-10 and I-40 is currently running.
Many roadhog types are running in the left lane full time as their personal lane and expecting others to stay out of that lane, so when we come up behind a slow truck and want to maintain my speed and time it to go to the left lane and pass when clear, the cruise control kills my speed way too soon.

So my options are to either slow and stay behind the trucks, do the speed manually or pull out into the passing lanes way too far in advance, none of which is what I want my cruise control doing.
The idea is nice in that it wants to avoid running me into a truck but it is more worried than works for me as it is almost scary to be running at highway speeds and timing the passing only to have it kill your speed just as you want to pull out to pass!
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Old 09-06-2021, 07:45 AM   #5
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It's one thing for the implementation to be poor (such as requiring adjustment of the spacing ahead).

But the problem with Sprinter-based RVs is that the system goes dead when driving on country highway roads for extended periods - which happens, especially in the western states when driving to parks.

And when it goes dead - it also takes along the active brake assist - which has the vehicle apply emergency braking if it detect an object ahead (such as an animal, vehicle or person).

We've had Toyota, Lexus and Tesla adaptive cruise control for years - and those systems have worked well for us - and haven't been deactivated automatically.

They will go offline when road conditions are bad (heavy rain/snow) - but when that happens the system just deactivates - and you can reactivate it when weather conditions improve.

But what MB has done is to disable the system completely - because the software believes it has failed. And it can't be manually re-enabled until the system goes through a new calibration phase. And there's no feedback provided by the system when it starts calibration or what is required to re-calibrate.

Maybe this isn't an issue in Europe - where they may not have lightly travelled roads like we have in the western US. Or they really just assumed Sprinters are used only in urban environments...
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Old 09-08-2021, 06:38 PM   #6
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Originally Posted by rprochnow View Post
And when it goes dead - it also takes along the active brake assist - which has the vehicle apply emergency braking if it detect an object ahead (such as an animal, vehicle or person).
To be honest I would prefer if I could turn off the active brake assist since I really don't much care for it, but MB does not give me that option. On the other hand I would prefer to not lose cruise control entirely so I will try to switch it on and off if I find myself on an empty road for any extended time.

It is optional in my car, a Honda Fit, and I generally keep it off.
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Old 09-08-2021, 07:27 PM   #7
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That could be considered a safety issue to me. I would also report the defect to NHTSA. They get enough complaints Mercedes won’t be able to ignore.
https://www.nhtsa.gov/report-a-safety-problem#index
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Old 09-09-2021, 07:28 AM   #8
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That could be considered a safety issue to me. I would also report the defect to NHTSA. They get enough complaints Mercedes won’t be able to ignore.
https://www.nhtsa.gov/report-a-safety-problem#index
It is not clear to me why cruise control not working would be considered a safety issue. It is identical to having a vehicle without cruise control and the government does not consider those to be safety issues.

Certainly not having CC would be a pain for me since I use it whenever I can, but if it fails I would not expect the NHTSA to issue a safety recall.
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Old 09-09-2021, 12:28 PM   #9
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Seems a bad idea to me to have adaptive cruise control fall back to standard cruise control instead of disengaging altogether. User expectations are that adaptive cruise control is keeping an appropriate distance for me and then suddenly it isn't? There better be some alarms going off to get my attention and tell me that I'm now responsible for maintaining distance. It's a better "failure" mode to disengage completely because it's better to have following distances increase unexpectedly than for following distances to decrease unexpectedly - and perhaps very suddenly and unexpectedly.

My guess for why the system disengages after a long period of time is either a software bug or an intentional time-out because a system that isn't seeing anything in front of it for an extended period of time might have a failure in it somewhere.

Overall, it sounds like a fail safe system. Any failure or potential failure errs on the side of not causing trouble.
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Old 09-09-2021, 02:28 PM   #10
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I think because it’s intention Adaptive Cruise control is a function to maintain a safe distance when using to maintain safety my guess
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Old 09-10-2021, 08:44 AM   #11
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Seems a bad idea to me to have adaptive cruise control fall back to standard cruise control instead of disengaging altogether. User expectations are that adaptive cruise control is keeping an appropriate distance for me and then suddenly it isn't?
I guess I disagree.

I don't depend on Adaptive Cruise Control to keep a safe distance between myself and the vehicle in front of me. I do that with my eyes, so I would prefer that if I have to have Adaptive Cruise Control and if it fails, then that it drop down to normal cruise control as that is what I want to use anyway.

In fact when driving my Sprinter on places like I-10 in Western Texas where traffic is light I usually disengage cruise control entirely if I find myself in other than very light traffic and, of course, I don't use it when the traffic is heavy, like when passing through large cities.
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Old 09-10-2021, 10:46 AM   #12
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I actually use adaptive cruise control 99% of the time when I am driving my personal cars. I will never buy a car without it. My first criteria I set when selecting an RV was that it must have adaptive cruise control. This is why my choices were basically limited to the Sprinter chassis.

I just took delivery of my 2022 View D which I will use to travel across the country for work purposes. I will be very frustrated if the cruise does not work as advertised.
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Old 09-11-2021, 07:21 AM   #13
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You can't avoid having the system go offline due to weather conditions (heavy rain, snow, ice).

But you should be able to minimize the risk of losing the system by briefly disengaging the system every 30-60 minutes.

If MB won't fix this flaw, it would be very helpful if they could at least document the algorithm they are using - and confirm what drivers can do to avoid having the system timeout and get disabled. And when that does happen, what the driver can do to minimize the time the system is down.

For now, my guess is: every 30-60 minutes without a vehicle in front, disengage cruise control by tapping the upper right button on the left steering wheel controls and then re-engaging after a few seconds. And if it does go offline, try to find someone to drive behind at a couple of car lengths until the system comes back, even if that means slowing down to make it easier for someone to pass.

Though... If enough RV owners complain to their Sprinter dealership and RV manufacturer (Winnebago, Thor, ...) - that might get MB to do something about this.
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Old 09-19-2021, 10:31 PM   #14
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I have a 2020 View J (2019 Sprinter chassis) that I’ve driven many miles on desolate roads in the western US and have never experienced the problems the OP describes. However, for a long time I would experience random shutdown of the cruise control, and it would then refuse to turn back on. Then I discovered that fidgeting in the seat was the cause (for example, reaching for something an arm’s length away), and I could immediately reactivate cruise control by pressing up on the resume toggle on the extreme left side of the steering wheel. It seems the seat has a pressure sensor that is very sensitive, and if you take your weight off the seat it deactivates cruise control. But the resume toggle makes it a breeze to get right back to cruise control. At least, that’s been my experience. YMMV…
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Old 09-19-2021, 11:03 PM   #15
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When we lose the cruise control, the system cuts out completely - displaying a message that adaptive cruise and brake assist features are disabled.

No action by the driver (steering wheel controls) or turning on/off the vehicle, will bring it back.

According to Mercedes, the system is working as designed.

I wish it was as simple as a seat weight sensor - unfortunately, it's more complicated.

Since MB hasn't (yet) documented what triggers the deactivation, all we can do is speculate. I suspect it is driving for 30-60 minutes on cruise control without any vehicles ahead - and that by taking the system out of cruise control for a few seconds every 30-60 minutes might prevent the deactivation.

Since we aren't planning any trips for a while in west Texas, we won't be able to test this theory any time soon...
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Old 09-20-2021, 05:41 AM   #16
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Quote:
Originally Posted by Mowind View Post
I have a 2020 View J (2019 Sprinter chassis) that I’ve driven many miles on desolate roads in the western US and have never experienced the problems the OP describes. However, for a long time I would experience random shutdown of the cruise control, and it would then refuse to turn back on. Then I discovered that fidgeting in the seat was the cause (for example, reaching for something an arm’s length away), and I could immediately reactivate cruise control by pressing up on the resume toggle on the extreme left side of the steering wheel. It seems the seat has a pressure sensor that is very sensitive, and if you take your weight off the seat it deactivates cruise control. But the resume toggle makes it a breeze to get right back to cruise control. At least, that’s been my experience. YMMV…
Mike, PNW summer, SW winter
Thank you.

We are on a trip now and the cc has disabled itself repeatedly and I had no idea why. But I think that at each time I was moving in the seat trying to position a cushion for my left arm and perhaps that was the cause. I will check today.
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Old 09-20-2021, 05:48 AM   #17
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Changing pressure on the seat can trigger the weight sensor, causing cruise control to be deactivated. I've seen this in our Sprinter chassis and other vehicles. All that's required to reactivate the cruise control has been to use the steering wheel controls.

The systems are programmed to ensure there is a driver in the seat while cruise control is engaged.

If this happens while just shifting around in the seat - the weight sensor may be too sensitive - but could still be as designed.

The problem we've been seeing is more serious - the system is completely disabled and cannot be enabled through any driver actions - which has caused us to lose cruise control for hours or days (until we find someone to drive behind for an extended time).
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Old 09-23-2021, 09:15 PM   #18
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Rprochnow,

Thanks so much for this information!!

We have a Sprinter based RV, 2021, picked up in June, which has been doing this “active distance assist inoperative” a few times/month since then. Cruise control would be disabled, then reappear in a random amount of time. I don’t like driving far without cruise control.

I took it to Mercedes dealer earlier this week for a software update, 3.5 hour drive. Since we were having this issue, they replaced the radar sensor. Drove home, feeling so happy to have unit working as it should, then, 2.5 hours into trip home, it happened again…oh, no. Cruise was disabled rest of trip home, one hour. Still disabled next day. Called dealer, bring it back they said, but fortunately I found your post before making the 7 hour round trip!

I drove to the nearest highway, waited for someone to go past, and followed him for 3 miles. Error message disappeared, and cruise control works again. I don’t believe I would have figured this out without your help.

I agree with you that this is so frustrating. I have a Honda CRV with adaptive cruise control—it does not do this despite being driven on same low traffic rural northern Wisconsin and Minnesota roads.
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Old 09-23-2021, 09:24 PM   #19
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What's especially frustrating is that Winnebago (and the other RV manufacturers) are unable to do anything about this - and USA Sprinter service will attempt a repair - but when it continues to fail, they'll give up and tell you it's working as designed - and there's nothing else they can do about it.

This is our first Mercedes vehicle - and so far, not very impressed with their software. And especially frustrated because there isn't any way for customers to contact Mercedes about issues.
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Old 09-24-2021, 09:05 AM   #20
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Originally Posted by rprochnow View Post
Changing pressure on the seat can trigger the weight sensor, causing cruise control to be deactivated. I've seen this in our Sprinter chassis and other vehicles. All that's required to reactivate the cruise control has been to use the steering wheel controls.

The systems are programmed to ensure there is a driver in the seat while cruise control is engaged.

.
I guess they though we were going to put the cruise on then get up and go make a sandwich?
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