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Active Brake Assist Functions Limited & Start Stop

3932 Views 4 Replies 3 Participants Last post by  mechatony11
Hi Guys, been scratching my head for a while with my 2016 GLA 45 AMG.

During diagnosis trying to get my start stop functionality to work as its never worked only once after a 3 hour drive it suddently began to work for 1 day. I replaced the secondary battery and still the same. Charged the secondary battery. no luck. I took it to a garage (noit mercedez) they ran some diagnostics and reported that the main battery was having issues. I never have received any fault codes on the display about a main battery and assume if it was low charge it would tell me on the display or warning/error codes. I think they reset the system and since then the Active brake assist functions limited now appears every time. I removed the 3 pin badge and there is a blank space behind with what looks like a place where a sensor should be. No wiring or anything. Looks like it has been removed before I bought the car or it was never there in the first place. I do remember the active brake assist working on the motorway as it beeped when cars were really close, but I understand there are 2 features that are similar for this functionality.

I have a feeling that he must have performed some sort of reset that has caused an issue here. Does anyones Start/Stop functionality work everyday for this particular model?

I was also told that if you disconnect the battery under the hood for 10 minutes it performs a reset which could clear up some of the issues.
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The star in the center of the grill. There are three different versions. One and most common is it is just a star with no function. Option two, the star can be lighted from behind the star. Option three is adaptive cruise control, where the car's speed adjusts to a car in front of you.

The brake assist has sensors in the bumper.
Thank you gbarringer, very useful information. Is there any way of resetting the alert for this without having to use a diagnostic machine? I have jet washed behind and on the sensors. I have read transport mode should be enabled and then drive for 10km to allow re-calibration but was unable to activate transport mode on my vehicle.
So more to this story - I had an engineer (non mercedes) run a full diagnostics with a good reader and he was going through the codes. Nothing he could do and he said that mercedes would likely need to do a software update on the car
I'm sorry for bringing up this old discussion. I had the same issue with the active brake assist function limited on my Mercedes, and it turns out that I had a damaged radar sensor. Search "Active Brake Assist Function Limited Diagnosis Mercedes-Benz on YOUCANIC" and you will find an article that goes over common causes and possible fixes.
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