need double check of OBD-II number P0158

Oh, forgot to add this is a Cali model. And the reason why I need calification is because online I see this

Oxygen Sensor at center cat. inlet (below engine) for Calif. model

at upper left cat. outlet (radiator side) for Calif. model

Left - Upper at left exh. manifold outlet (radiator side) for Calif. model

And I know there are four, because an Autoparts dealer said so (is this correct). So I'm guessing that front / after the converter would be "upper left exh"?

You missed one;

The 99 california Maxima has 4 O2 sensors. One before and one after the cat plus the 2 in each exhaust manifold.

I find it rather odd that the downstream O2 after the converter has gone bad. Usually its the ones in the exhaust manifolds that go first.

Your info is good, though.

CD

Thanks codifus, but I'm even more confused. the online o2 stores show

So there are 2 after the catalyst, left and right - which one should I replace? I guess I could just do them both (about the same price, right does cost $4 more). Does Left and Right mean L/R location of the car? Thanks again

Had the same on my 2000 Ca - both bank sensors needed to be replaced, and the cars computer flashed to reflect the new sensors. Had that done at the dealer - not cheap, but fixed right.

Not sure your 99 is the same - but just replacing one sensor may not fix your problem.

and to all you "the dealer is always a rip off" former "terminated by a Nissan dealer pseudo mechanics" - save your dam worthless flame posts.