Active brake assist function limited.

[DJ85]

This has started to appear on my dash last few days on my CLA has anyone came across this? Looked online and seems to maybe be a dirty sensor but I've tried to clean all sensors i can find but still comes up. Also tried turning assisstedbrake on/off on my wheel and still nothing. I think it's a radar sensor going by what I'm reading and also been told to clean my windscreen but not sure what that would do? Way to take it through the car wash and see if that makes any difference.
Just looking for any advice before I put it into the garage for a £75 hook up to diagnostics.

 

[paradigm]

been told to clean my windscreen but not sure what that would do?

Pretty sure most cars use an array of sensors and cameras around the base of the rear view mirror. So a filthy windscreen will impede their efficiency/effectiveness.

 

[DJ85]

I've gave the windscreen a scrub and didn't seem to help anything. I noticed a smelly tree hanging behind the Mirror to which I removed and still the error comes up.