Just had mine replaced in the 98 e 430. Was running fine but the engine light came on. Done under warrenty. They told me all it takes is a fine piece of sand or dirt to go on this censor to make it malfunction. Also keep your air box clean on the inside and make sure all conections are proper leading into the intake and that the filter sits correctly with no gaps.
98 E430(sport), 99 ML 320 (sold) , 05 C 230(sport) Mark