I know you probably already did this...but my 4Matic light was on. Turns out the transmission fluid was too high. Then, I unplugged the battery for about an hour and it went off.

It occasionally comes on at acceleration from a stop though.

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2004 E320 Wagon W211
2000 CLK430 Convertible W208
1985 300SD W126
1983 300D W123