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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?

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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.

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  • thanks for the info. So you mean to say that there might be a DTC stored as potential fault code (mode 07). So Mode 01 PID 01 will store as MIL NOT Commanded ON & codes ARE stored. Am I understanding it right?
    – Soumya Sen
    Commented Nov 11, 2016 at 9:31
  • @SoumyaSen yes that's right
    – Zaid
    Commented Nov 11, 2016 at 10:21
  • Thanks. But here's the doubt then, P0261, P0118, P1696 were the fault codes that appeared in mode 03 (current fault code) and DTC count came as 3 (in mode 01 PID 01, bit A6-A0) as expected. But MIL commanded was OFF (in mode 01 PID 01, bit A7). When I looked at the dashboard, the CEL/MIL was glowing. How can MIL commanded be OFF?
    – Soumya Sen
    Commented Nov 11, 2016 at 11:46
  • @SoumyaSen I have no clue why this would be the case
    – Zaid
    Commented Nov 11, 2016 at 17:15
  • which are the difference between mode 03 and mode 07? Sometimes mode 07 show me more trouble code...is better to use only mode 07 or all two? For reading trouble code.
    – Dario
    Commented Nov 10, 2017 at 11:35

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