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OBD-II Mode 01 PID 0 gives commanded MIL on (bit A7, see link) and Number of confirmed emissions-related DTCs (bit A6-A0, see link).

I did hit Mode 01 PID 01 on a few cars but got surprising results. In Skoda Superb, there was no visible Check Engine Light (or MIL) on, there was no commanded MIL ON (bit A7), but DTC count (bit A6-A0) was 16. How is it possible? If the commanded MIL is not ON, how can number of DTC count be non-zero?

http://www.epa.ohio.gov/Portals/27/echeck/docs/MIL%20Cmd%20and%20Trouble%20codes%20Yr%202010.pdf

Going through this website, MIL NOT Commanded ON & codes ARE stored = 0% cases. But the case in question is actually this case.

Side question: MIL Commanded ON & codes are NOT stored. Is this case possible? If yes, when can this case happen?

dlu
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Soumya Sen
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1 Answers1

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Not all DTC's will activate the CEL

It is up to the manufacturer whether or not to trigger the Check Engine Light based on the Diagnostic Trouble Code, so a misfire DTC is not the treated with the same severity as an idle-control DTC.

In fact, the same make and model manufactured for different markets (Europe vs US) can have sets of triggers, as is the case with the BMW E39 5-series. The variation here is very likely driven by differing motor vehicle legislations & requirements.

Zaid
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