Well, after 2 times of my code being zero, I finally got a valid code on my 2000 SE. It's 0420 and the description is, "Catalyst System Efficiency Below Threshold". So, what would that mean in laymans terms? Can I fix it? I really hate going to the dealer unless I have to.

Thanks a million,

Bill

 

If you find out let me know too. I have the same one!

What exhaust mods do you have?

 

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I seem to recall a post sometime about the tolerances being to tight and it needs to be "reprogrammed" to loosen them up....Sorry, thats all I can give ya.

 

Yeah, it is a "Catalyst" code dealing with your 02 sensors. Mine was because of a bad flex section. But, you could have a "regular" exhaust leak if you have changed anything underneath...ie Y-Pipe, Cat, Etc.

http://forums.maxima.org/showthread....hreadid=118330


Hope that helps...


ADMAN

 

I also have the same problem, and my exhaust consist of a Stillen Y-pipe, and RT CAT. So does this code mean that my Y-pipe has a leak, my RT cat flows too much air, my O2 sensors are bad (if so which one), I am kinda lost on what needs to be done to correct this. Thanks

 

Well, unlike most of you guys (and girls), my car is bone stock
So, I would have to guess it's what a few of you have said; catalyst, o2, or maybe just a whacked ECU.
Thanks for all the info and help. This gives me a little more ammo when I visit Mr. Service Manager!

BTW, here's some info I found for anyone else who may be having the 0420 code:
Make: NISSAN Model: MAXIMA Year: 2000
Service Bulletin Number: NTB00070A Bulletin Sequence Number: 199 Date of Bulletin: 03/01

NHTSA Item Number: 619999
Component: INTERIOR SYSTEMS:INSTRUMENT PANEL:GAUGE:INDICATOR
Summary:

SOME VEHICLES MAY EXHIBIT A MALFUNCTION INDICATOR LAMP ON WITH DIAGNOSTIC TROUBLE CODE P0420 (THREE WAY CATALYST FUNCTION) STORED IN THE ECM. *TT

Thanks again everyone,

Bill
2000 SE (bone stock)

 

had that on my 2k @ 34k, dealer reprogram the ECM.

neil