2012 Corolla Base L - Why does resetting the ECU via OBD2 bluetooth device cause it to test differently vs taking off battery cables?

[Jesse106]

I've noticed this lately and I'm more so curious as to why. I have a BlueDriver bluetooth scanner that allows Live mode diagnostics, Mode 6 to see what has tested and what hasn't in real-time, etc. I have noticed that when I reset the ECU with the bluetooth device (you go into the "Clear All Codes" mode even if there are no trouble codes pending anywhere), it starts retesting things in a different order vs taking battery cables off.

For example, I have even reset while going down the road using the bluetooth device. As soon as it clears all of the codes, then the ECU starts immediately testing. The car doesn't skip a beat and there is no noticeable sound or testing, but a large number of "misfire" tests occur while driving and all are just as good of a result as if testing sitting still in the driveway with it in park and running (0 misfires on both). Compare this to if you take the battery cables off, the misfires will also test first, but the car will start and sputter out the first time and you'll have to crank it back up again and that was the same misfire tests testing. Why doesn't it sputter going down the road? The misfire tests the same way with the exception of the sputter. I'm kind of curious why it is different for all of this stuff based on how you reset it.

Next, the upstream O2 sensor partially tests, the VVT, Purge Flow Monitor, Fuel system, etc, will test. Then the O2 sensor. They test in a different order if taking the battery cable off in the driveway vs resetting the ECU via the bluetooth device while either parked or going down the road. Why would they test differently based on how it is reset? Now I'm just curious in general.