i find it rare that i learn something i just come across by accident. so watching this in the back ground of doing other stuff on facebook(it's pretty boring to watch, designed for his students)
he mentions the O2 sensor, and it' makes perfect sense to Me in Hindsight .. if you have an O2 sensor ERROR CODE, it could be related to other things, not the sensor, eg, intake leak(hose off, crack, gasket,) or injector out of range, blocked, or spark plug dead even....
i never thought of this happening, and haven't read it when people have been changing O2 sensors due to codes and still having codes.