clive

The CEL has been lit ever since I bought the car 3 months ago. Oxy sensor #1.
I hadn't got around to replacing it yet because there were more important problems to deal with, like the multiple oil leaks, ancient air filter, ancient plugs, filthy TB, and so on.
The last thing I did was oil the door hinges. Evidently the car must have felt specially grateful because when I drove off, I noticed the CEL was dark, and so far, has stayed that way. Of course I checked, and no the bulb hasn't burned out. So it appears the defective O2 sensor has fixed itself. I wonder for how long?

99grnmaxgxe

iTrader: (11)

I don't think the 02 can fix itself, there is probably some other explanation for that.

Ridge Runner

I think O2 sensors slowly lose their effectiveness, and if the ECM reads three cycles without a fault it clears the CEL. It will very likely come on again.

clive

How long is a 'cycle'?

Ridge Runner

It's not real clear. Per the FSM:

The light will go out if the vehicle is driven three times with no malfunction. "The drive is counted only when the recorded driving pattern is met (as stored in the ECM)."

The ECM stores driving conditions the first time a fault is detected (fuel system status, calculated load value, engine coolant temp., etc.). I assume these conditions must be met again, so a "normal drive," like to work and back, might suffice.

clive

Interesting! Thanks! How very very obscure... anyway the CEL remains off. Bearing in mind my experiences of Nissan harness connectors (crummy) maybe it was a connector fault in the first place. I'll wait and see, meanwhile I am grateful I can carry on with the next jobs in order of importance.

nabeel19

yeah, I cant imagine a sensor fixing on its own, that would be great though I would think a lose connector was the culprit

zander

iTrader: (2)

I hate freaking sensors, all of them, one goes bad and you car runs like crap lol! Could the code have been there because the car was so out of tune?

clive

- you know, I was beginning to think the same thing. This is a car that shows signs of having had no proper maintenance since, ohhh... about late 97 I think. I found a Nissan sticker on there for the 1 year service and that was it. I guess it was super lucky that it was pissing oil everywhere (PS pump and motor) so that at least its evil owner had to put new oil in ... otherwise I imagine the motor would've been like a cheese grater by now.
The air filter was solid... can you imagine a 9 year old air filter. Original plugs with 75K at least on them. The TB was filthy. The IAC and PCV I haven't got round to, yet. The MAF mesh filter was full of insects and stuff. I don't think the motor had been cleaned since new.
It ran like cr*p when I bought it. A constant trembling. And consumed huge amounts of gas. But now, even with some work still to do, it goes like a rocket and uses not much gas. So I have been wondering, if the O2 sensors haven't been sooted up over the years because (mainly) of the choked air filter and MAF. And then, after I begin maintenance and it starts to run lean, could it be the sensor burns off enough soot to start functioning properly? I dunno. I suppose the test will be, how long it stays working. I had better replace the PCV and clean the IAC before anything happens...
-
oh, btw, I also hate sensors. It has been a major technology shock to me, to have to deal with suchlike. I am used to driving cars with contact-breaker ignitions and carburettors, 100 octane leaded gas, and not a sensor in sight.

Mr. Blue Sky

iTrader: (1)

no sensor lights going off, but a ton of vaccuum leaks. Need to redo vaccuum lines.
BTW, never heard of self fixing sensor. Would be sweet though

MikeinMadison

Your thinking on the O2 sensor is quite plausible. Are there any tried and true strategies for improving contact in the connectors? Pretty small spaces...

clive

I'm happy to say that the oxy sensor fault has not returned and the car is still running great. I'm pretty much convinced that the sensor had been sooted up by the choked air filter. It was drinking gas before, and now it seems about average for a Max, though I have to admit I am a quite aggressive driver. (Have to be, in this town: the streets are full of Beemers and 3.5 Altimas and 5.6L V8 pickup trucks and so forth. We have a definition here for the microsecond: the interval of time between the lights turning green and the person behind blowing the horn.)
Therefore, I think that when taking on a used Max (or anything else) for the first time, do all the routine maintenance before thinking of changing any sensors. Saved me over $100.