....reset the code after changing the fuel filter? I searched yesterday on "check engine" light and came up with either a filter or an O2 sensor being bad. The typical symptoms (from the thread) are not happening, poor economy, "rich" exhaust odor, poor idle, so I figure the filter. I read and printed Steve Brotherton's piece in DIY and have an idea of what to do to reset, multimeter is in top tray of my toolbox.

Thanks in advance and many thanks to all who help each other out in this forum.

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1991 300SE (my ride, 279,000 miles, looks almost new
1954 Cadillac (21 yo son's car, he bought when age 15)
1972 SeaBird 19 ft runabout (old but solid, slant six, Volvo sterndrive perfect condition, undergoing complete overhaul and refit)
1998 Toyota Rav4 (my sons daily driver when he is in the Continental US, PROUDLY serving in US Navy)