My SES light came on a few months ago [2000 Max SE] so I took it to Autozone and they said it was the oxygen sensors bank 1 I think. I had a friend of mine check it too(mechanic) and said the same thing. He also said its better to just change out all 4 at once cause if 1 is bad the others are about to go and its better to take care of it all at once?(True or not???)
SO THEN
I said I'd think about it and he reset the ECU and the light went off but he said it would probably come back. Now its 3.5 months later and the light has never come back on??? Does this mean the sensors were fine? maybe just got shaked up or something? Anyone experience anything like this?

 

I had SES light on for a month or so.Yesterday I changed oil and air filter and this morning SES light goes off.weird. I wonder how long take to turn on again, hope never :d
oo and the code i had was po420 or something.

 

That is strange. I have yet to have an SES light come on. I can say though my 97 Grand Prix would do this but only if I used crap gas. Anyway, guess i'm lucky as are you, i'd say if it doesn't go on then you saved some cash. Only question is, isn't this technically considered environmental. An Cat is usually covered under Federal Law, from what i've been told, that you can have it replaced free if it goes between the 10/100,000 mile warranty. Chris

 

8/80 not 10/100 and no, O2 sensors aren't covered. It's all spelled out in your warranty book.

 

Thanks DanL, didn't know it was in the book, never looked for it. Chris