rules on MIL

I am wondering what exactly the rules are for MIL to come on on a OBD II system.
For example what makes the same exact failure code set to have MIL on at one point in time and MIL off later.
The example code set that gave me MIL on for while, then MIL off for about half day and then MIL on again is P420 Confirmed P301 Confirmed P302 Confirmed P303 Confirmed P304 Confirmed P300 Confirmed P420 Pending
By the way what exactly is the difference between confirmed and pending in a scanner (in particular for ACTRON CP9575) ?
And which one is more recent?
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Depends on the monitor/system being tested. You can Google this.

If the monitor runs and fails so as to turn on the MIL, then the MIL will remain on until the test succeeds the next time it runs.

You have a /massive/ misfire of some kind. With that collection of codes, I'll bet you have some very obvious symptoms, like stumbling and bucking.

Confirmed/pending should mean the two stages of 2-trip logic codes. Didn't your scanner come with a manual, or at least a URL to one?

"Confirmed" is more recent. It means a 2-trip logic test failed on two successive occasions.
What kind of car is this? Make? Model? Year? Transmission? Drivetrain? Trim level?
--
Tegger

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Thank you Tegger.
The car is 2001 Honda Civic EX Coupe, at about 171,000 miles.
There are virtually no detectable misfire symptoms in the engine. It is running almost like a new car. Perhaps with some exhaust noise, I am not sure. Many people drove the car. They expressed there is perhaps misfire but they were not sure.
All monitors were always on when this MIL On,OFF,On happened. That is why I was questioning what I am seeing.
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