O2 sensor Q's - checked FAQ already

[bowyer2002]

I have 138K miles on my Tacoma and wonder if I need to replace my O2 sensors?
No CEL yet just wondering if these are PM items or do you replace them after the CEL comes on? They're not cheap but any extra mileage I can squeeze out will help.

 

[WristPin]

when an O2 sensor fails it will turn on the CEL. it is a priority code, which means that it affects the run mode. It will go into limp mode which sucks down the gas.

Check your owners manual to determine if it is scheduled maintainence . Some vehicles mention it. I dont own a taco so I dont know.

 

[Duane]

I think that I had this discussion last year some time..will look through my old threads.... I think someone had mentioned that an O2 sensor may become lazy or lets say wander in a larger range as time goes by without tripping the light.
This being said..yes I sprung for a new one around 250,000 km and it didn't seem to make any difference... on my 96 runner 2.7 litre

Therefore I think it is pretty much a run to failure device.

https://forum.ih8mud.com/95-gen-toyota-trucks/163680-96-2-7l-o2-sensor-when-replace-how-much.html