I have a 2000 S430 with 90,000 miles on it. my check engine light has been on for awhile. i've taken it to my mechanic 4 times for the same thing. initially the codes read Mass Air Flow Sensor, so of course they changed it but it came right back on in less than a day. i took it back and they replaced the part but the light came right back on. Has anybody ever experienced this before? If so, what was the outcome?