PROBLEM SOLVED !!!!

Resolved by clearing the codes, nothing else.

Was extremely difficult to clear the codes by hand, using pin 21 and the procedure of reading, reading, clearing, reading, clearing, etc.

The sequence of clearing the codes was important, the codes cleared from higher codes to lower. I had to read (and patiently wait) each code in the sequence then wait for the last code, clear it, then turn ignition switch off, start again read all the codes until the last one, clear it, ignition off... you get it. When I tried to clear the codes from the first one up it would not work.

In all, solving this problem took over 10 hours of work, no to mention the incredible frustration. All this for simply changing a bad battery.

Looks like an ideal class action case against Mercedes to force them to reset these vehicles for free at the dealer. Just plugging the scanner and hitting "clear" would have solved the problem (at $150 at the dealer...). A problem that is just due to bad design on Mercedes Benz part (a simple "clear codes" button function in the cars would eliminate this inconvenience). It's a shame that the dealers use this as an opportunity to plunder and pillage.