Your information conflicts with the information that I have Eddie. Our local Merc dealer told me that from 2018 you wont even be able to open the bonnet of the car without a code reader and that code reader cost the Merc dealership £175k. Whats more its not done by a stand alone lappy but on a link to the computer back in Stuttgart. The local Maserati dealer has a similar arrangement - any diagnosis is done on mainframe back in Italy.
The Ynaks have made it law for some basic codes to be available to all but the manufacturers have lots of other dcodes that you cant get at on a generic reader.
I havent tried getting any reverse engineered code for the Merc but I have for the Ferrari and I have failed.
