C class Coupe (c300)
 

Warning messages on dash:
-- Traffic Sign Assist inoperative
-- Active Lane Keeping Assist inoperative
-- Pre-safe functions limited

Mercedes Brentford are telling me the above messages show up because I'm in Sport+ mode. It does kind of make sense but at the same time why would the safety features turn off? If anything you'll need them more because you'll be driving it that but harder...

According to the 2017 C300 Coupe manual, for all of those actions the solution is: "Visit a qualified specialist workshop."

No where in the manual does it mention that those functions become disabled in Sport + mode. If they claim it does, I would recommend asking to see the documentation (workshop manual or users manual) that proves what they are claiming.

Next, I suggest going to another dealership or shop.

+1

Your dealership's a really crappy one.

Find another dealer. These functions aren't supposed shut down just because you're in Sport+.

i have this warning comes up, and i'm NOT in sport+ mode.
i noticed it mostly show up in the summer, when the weather is hot.
i complained about this on 20,000 miles Service B, then told them again at 30,000 miles Service A. i still getting this message even just after a carwash.
i planning to going to different dealer to do my 40,000 miles Service B.

Do you have things like sprint booster (pedal booster) installed? If you do, it could be one of the reason the warning message is popping out. Otherwise, I would think that you have a sensor malfunction related to the pedal.

The messages all relate to a malfunction of the cameras used to track lane markings and read speed limit signs. Since Presafe relies in part on data from those cameras, the system cannot perform reliably and shuts down.

Return to the dealer and advise they need to connect the car to a Diagnostic terminal and see the specific faults presafe is throwing.

Their first answer was uninformed and pathetic.