Back in Jan of this year my check engine light came on. I checked the codes and discovered it was the rear o2. I reset the ecu and everything was fine for about a month. Then it came back on, same thing. Reset it. A couple more months went by then it happened again. I reset it and everything was fine until last week. The car runs fine, I'm not trying to replace it until it becomes a problem. I have noticed that it appears to come on when there is moisture in the air. I'm in La Mesa, CA. It's mostly dry and sunny. When I visit Oxnard, CA the marine layer creates a much more humid environment. 3 of the 4 times it's come on has been either in Oxnard or on the way back from Oxnard. I go up there about once a month. Could humidity have any effect on the sensor? From my searches here, I don't have much to worry about if the sensor continues to do this. Any thoughts?

 

Well, if the sensor gives you repeated codes...it's bad.

That's all there is to it.

 

Yep, all that tells you is that it's a gradual failure, probably due to foul-up or something like that (instead of a wire snapping or the heating element failing for example). I left mine for a long time because it doesn't affect engine performance in any way, but sooner or later you'll get too annoyed with the CEL to leave it any longer

 

My light has been on for about 6 months now. . .

I already replaced one of the front sensors. Maybe eventually I will get around to finding out what is wrong with the other one.

 

Yes, I ran my rear O2 sensor until it completely failed! I kept resetting the CEL until it would'nt reset any more. As soon as the sensor died, the CEL recognized it being non-functional. I, say, I went about 8 months on doing this until I replaced it. The only way I noticed any difference in replacing it with a new one was the gas mileage. Other than that, the bad one didn't affect engine performance. What the computer does if it notices a bad O2 sensor is that it will revert to an "open-loop" fuel control in maintaing the air/fuel ratio.

 

Thanks guys. The timing doesn't seem to be gradual. But...when I get tired of resetting, I'll replace it.

 

reseting the ECU doesnt mean you fixed the problem. Running with a bad o2 is alright as long as you know youre cutting back on the fuel economy. If you want to try cleaning the sensor, you can take a torch and burn off the carbon build up, but the best thing you can do is to have it replaced.

 

I have a 95 and a 96 Maxima. I have replaced oxygen sensors (as they fail) with the generic $41.95 ones from www.oxygensensors.com. You have to splice the OEM wiring harness from the old OS (three wires), but they work great and cost a BUNCH less than OEM.

At that price, why wait?

 

i replaced my rear right side few weeks ago and i dont notice any mileage improvement at all. why is that? all of my sensors are new and have been changed except the rear left side one. why no good gas mileage here ?

 

is your car running rich?