Reporting a software fault on a B250e

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gbCambridge

New Member
Joined
Apr 7, 2014
Messages
22
Car
B250e
Hi,
I have owned my 250e for about 6 months and I am still discovering "features" in the SatNav and Cruise logic. Here is something that I just found...it seems like a fault..but you tell me.

Assume that you have set up SatNav for a journey and that you are using cruise control. At a point on the road, the SatNav tells you to take the next exit, where the exit road meets a roundabout, and where you should take a certain exit (which one does not matter).

Now let's assume that you know better and decide to drive straight on. What appears to happen is that the SatNav is not aware of this decision and goes through the motions as if you had taken the exit, which involves slowing the car down and twitching the steering for roundabout crossing. This can be a bit disconcerting for cars following as they see no need for you to slow down.

I have not tested my solution yet, but it involves disconnecting the cruise when I decide to ignore road instructions and reconnecting it when the exit (or whatever) has passed.

So, is this a bug or a "feature", and in either case where in Mercedes do such things get reported?
 
My guess is that the car is trying to make you aware that you're taking the 'wrong' exit, but I have no idea if it's a configurable option that can be unticked.
 
So, is this a bug or a "feature", and in either case where in Mercedes do such things get reported?
What you have described (I think) is that you're travelling on a road - probably a dual carriageway - with a roundabout either above it on an overbridge, or beneath it with you travelling over the roundabout on a bridge above.

If that's the case, then it's simply a function of the sat-nav not being able to resolve the vehicle's actual position in relation to the exit and the subsequent roundabout vs. what it was advising you to do. If that's the case, my view is that it's simply a system limitation rather than a software fault.

FWIW, I noticed that and A250e and an EQA350 that I've had as loan cars have a feature whereby the car uses sat-nav positional data and the installed cartography to anticipate the need for braking at upcoming road features such as junctions, roundabouts and sharp deviations, and it sounds like the experience you describe is an extension of that capability. As they were loan cars I didn't bother looking into the settings to see if it could be turned off.
 
What you have described (I think) is that you're travelling on a road - probably a dual carriageway - with a roundabout either above it on an overbridge, or beneath it with you travelling over the roundabout on a bridge above.

If that's the case, then it's simply a function of the sat-nav not being able to resolve the vehicle's actual position in relation to the exit and the subsequent roundabout vs. what it was advising you to do. If that's the case, my view is that it's simply a system limitation rather than a software fault.

FWIW, I noticed that and A250e and an EQA350 that I've had as loan cars have a feature whereby the car uses sat-nav positional data and the installed cartography to anticipate the need for braking at upcoming road features such as junctions, roundabouts and sharp deviations, and it sounds like the experience you describe is an extension of that capability. As they were loan cars I didn't bother looking into the settings to see if it could be turned off.
Hi, thanks for the analysis...coincidentally my car goes in for a software update today...a safety recall on steering problems and I hope to find someone able to discuss this feature that I "discovered". The most alarming part is when the car slows down on the motorway for no obvious reason, except the car thinks I am approaching the roundabout on the exit. Anyway, as we are going to France in a few days I shall have ample opportunity to test my "fix", which is turning off Cruise when I deviate from the Satnav path, and resetting it after I have left the exit behind. This shows how frail is the system for the car "knowing" precisely where you are...unlike for parking, where I am serenaded by beeps, burps and worse.
 
Hi, thanks for the analysis...coincidentally my car goes in for a software update today...a safety recall on steering problems and I hope to find someone able to discuss this feature that I "discovered". The most alarming part is when the car slows down on the motorway for no obvious reason, except the car thinks I am approaching the roundabout on the exit. Anyway, as we are going to France in a few days I shall have ample opportunity to test my "fix", which is turning off Cruise when I deviate from the Satnav path, and resetting it after I have left the exit behind. This shows how frail is the system for the car "knowing" precisely where you are...unlike for parking, where I am serenaded by beeps, burps and worse.

Ask them to also update the COMAND firmware to the latest version (this updates the the infotainment system and navigation software, but not the maps), unless obviously its already on the latest version. Even if it won't fix the issue, it can't hurt.......
 
My guess is that the car is trying to make you aware that you're taking the 'wrong' exit, but I have no idea if it's a configurable option that can be unticked.
Yes..and it is also making the car behind me aware...as I slow down to 15mph on the motorway! I am going to chase MB on this..it should at least be mentioned in the manual/guides.
 
As already mentioned the moving GPS location isn't precise enough to know that you've ignored the selected route by not taking the slip road - this happens on all satnavs. They generally 'realise' as you pass the roundabout, where your deviation from the expected position is significant enough to trigger a route recalc.

The issue is with your cruise control - disconnecting this and resuming it a few seconds later would avoid the problem. Moving to the right hand lane before passing the exit might also help as it would increase your distance from the slip road, helping the satnav to spot a bit earlier that you're not now heading for a roundabout.

Again, there may well be a menu option to disable or 'tone down' this auto-braking behaviour ... I would check this thoroughly before raising it as a problem. For example our car has Active Brake Assist which can be set to 'early', 'medium', 'late', or turned off.
 
Well, Mercedes responded to my description of the problem by simply restating the problem and saying that the driver is responsible for the driving of the car. Pretty well what was expected. i am used to the feature now..which may make switching to other cars a bit tricky, at least at first.
Thanks for the advice on this ...I wonder if Tesla vehicles have similar experiences
 

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