Yes, this is fairly common, and not just on Mercedes either. The MB description is "self-adaptation at partial load at limits", I believe the description you listed is the generic OBD II description. The fuel trim is a shift in the operating limits of Lambda control. It takes several things into account, one of the important things is the air mass being sucked in by the engine. If the mass air flow sensor is incorrect, the fuel trim will reach a point where it says "Whoa, I can't compensate for this amount of air any more!" and will be unable to shift any longer without really having a whacked out mixture. It's really up to the technician to decide why this has taken place, there are several other reasons, but the air mass sensor is definitely the cause du jour for this code. How many dozen times do you need to see this code and have it be because of a bad mass air flow sensor before the technician can simply see the code and recommend an air flow sensor???Gilly

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