Engine Control Light

If the Fuel Cap was the only problem, the Check Engine Light should go off by itself with in 2-3 days. Did you get a genuine Mercedes Cap? Is the filler neck distorted in any way, so the new Fuel Cap does not seal? Good Luck!

whoever repaired your gas tank did not do it correctly IF the light is caused be fuel tank not passing integrity test performed semi randomly by engine ECU . This type of code will self clear if system is actually ok ( like if u left the gas cap off then drove away ) after 4 sucessful gas tank tests.. the system (as required by EPA standards) actually appiles vaccum to the gas tank and then see's if the pressure sensor says its holding vaccum (after shutting the main vent located NEAR THE FILLER NECK inside the right rear fenderwell.... i know its acomplicated answer but i hope u understand it alittle..all this to keep vapors from leaking into atmosphere which is a good thing