I haven't had your issue, but from googling around the Mercedes Benz forums, it sure looks like you need someone with the STAR system to clear it for you. Sorry to say that. Below are a couple of cut-and-pastes from other forums:

"I think your going to have to have it re-set by someone with the STAR system... I just had this same problem... I was having problems with the trans going into the soft limp mode where it stays in the last gear it was in until you shut the car off and restart. (Classic Conductor Plate Failure...) I out smarted myself by trying a coasting re-start. That was the wrong thing to do because it locked me into hard limp mode... All I had was 1st gear & reverse. I changed the conductor plate and still had the problem. I had to have the car towed to a local private repair shop that has the STAR system. $75.00 later the code was out and everything was back in order. So long story short, once your in the hard limp mode you need the STAR system to reset that code. Good luck and check with a local private shop that will save you money over the dealer."

"Transmission codes cannot be cleared by a hand held scanner. You will need Carsoft and adapter. It's easiest to just drive to a reputable independent mechanic and ask them to clear the fault. My indy did the tranny clear for $35 after I replaced the conductor plate - and he even gave me a printout of stored codes."