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Old 03-08-2003, 09:40 PM
Senior Member
Join Date: Sep 2002
Posts: 2,486
A faulty MAS will not necessarily turn on the check engine light overnight! The air mass quantity becomes more inaccurate over a period of time. The engine control module(ME-SFI)adjusts fuel"TRIM" to compensate for the erroneous air quantity data. When the MAS degrades to the point where the ME-SFI control module can no longer compensate for the inaccurate air mass data, the CHECK ENGINE light comes on. This data can be checked to determine the efficiency/function of the MAS, well before the CE light comes on. It sounds like the technician who did the "B" service on this car took the time to check this, and probably saved the owner a trip back to the dealer. As for the transmission work, it could be the dealer was making sure that the transmission was good-to-go while it's still under warranty.
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