Something to keep in mind, MB uses % off for the duty cycle readings. The resr of the world, including Craftsman, displays % on. Subtract your meter reading from 100% to get the MB codes. I.e. a 30% reading on your meter is really 70% in the MB error codes book.

If the reading is flutuating while the engine runs, it means that your O2 sensor is working and the fuel injection is in "closed loop" mode. That's a good thing.

ETC = Et cetera, Latin for "and other things"
ECT = ???

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Norm in NJ
Next oil change at 230,000miles