A/F/R gauge for tuning

Rat Bastid said

What happens when you get a lean miss????? What do you think the O2 sensor will say?

That’s one quick example of how an O2 sensor can lie to you. It’s a dumb tool. It can’t think. You have to think for it and not take everything it says as gospel.

Also, you can run into reversion issues which will make the O2 sensor tell you fibs.

Click to expand...

To this point, I watched a guy diagnose a rough idle one a newer car using some fancy gizmo. Easy to see in the wrong hands it would be a disaster but this guy understood how the O2 sensor worked and the tool had was able to tell him the duty cycle of the sensor. Turned out to be just on the fair edge of tolerance from age. As I recall, all the signs pointed to something else (don't remember what) but knowing the tool AND the proper operation/operating characteristics was key.

So again, to your point, a person still needs to know some stuff and not rely on the tool to tell them what's wrong. It's an indicator in a pile of other indicators.