So, what's my problem??

[Ivan]

Your '98 will actually have 2 - O2 sensors. An upstream one ($65) by the exhaust, and a downstream one by the cat ($119)... Yes, those are NAPA prices too...

There is a way to test your sensor too... Just do a search on "test o2 sensor", and lot's will pop up...

Ivan

 

[nitrogt101]

Cool, thanks. Yeah, I know there are 2. It is the downstream one that is not reading right. The computer adjust to the upstream one, this sensor is just for smog regulations/checks I guess. I'll do that search, thanks again.

 

[Sarge]

On most vehicles the CE light is only lit if a piece of smog equipment is bad so in the future that would narrow the range of search. I've personally had it come on for the O2 sensor, the gas cap being loose and a plugged air filter (caused bad readings at the O2 sensor).

Sarge

 

[Spazz]

The 2nd O2 sensor basically monitors the efficiency of the Cat (AKA Catalytic Monitor), If too much O2 or to little O2 is released out of the cat, it will throw a code indicating the Cat is bad, or is on its way to the grave. The Upstream O2s will compensate some for the downstream sensor, so if the wiring is damaged, it may think you are running too lean (if wires are damaged or the Cat isnt using up enough of the oxygen) and try to correct the situation with a richer air/fuel ratio. A hole or crack in the exhaust system could also mimic the same symptoms with too much fresh air getting into the exhaust and the second O2s sensing it.

Water can also damage the sensors..