I'm in the process of buying a w205 c63s. Found one with all the specs I want. The car seems faultless.....except for one thing. Sometimes after startup it shows the message: "Rear electronic diff inoperable". The guy said that he's been to mercedes twice, they upgraded the software but after a while it does it again. He said he's not bothered too much about it because the car still works perfectly fine and he knows of others that have the same issue, but drive without any problems.
any suggestions on the matter would be greatly appreciated, and also if there's other things I should be on the lookout for. Thanks