Question about O2 readings

[blackgn231]

they seem to be all over the place when driving from down in the 100's to 600's is this a sign of a bad O2 sensor? But have been wondering about this. I have the 2.1 scan tool anyone on this?

 

[dennisL]

Its normal for the O2 readings to be "all over the place" while driving. The only time they don't jump around is during WOT.

The ECM causes the O2 readings to go up and down. When rich (O2 above ~600mV), the ECM makes it lean then it turns right around and when it sees lean (~500 mV) it makes it rich. It's a little more complex than this but you get the idea.

Dennis