SES p420

[Amosnorider]

My 2000 I 30 has been throwing this catalyst efficency below threshhold code. I heard many people get this code. Wondering if anyone was successful at resolving the issue. The code will turn itself on and off evey couple fill-ups. I have been using shell 91 for fuel. I replaced the gas cap since the code was turning off by its self. So I'm thinking my cat is ok. Anyone had their computer reprogramed at the dealer?

[audtatious]

Possible Causes:- Three way catalyst (Manifold)- Exhaust tube- Intake air leaks- Injectors- Injector leaks- Spark plug- Improper ignition timing

Check the plugs and injectors as those seem to be the more common issues with this code

[matt.sliger]

I have a 2001 Nissan Maxima. It is doing the same thing throwing both the p420 and p430 codes. He is right those could be the causes but your car is a 2000 so face it they are most likely toast. I always run the 91 octane, etc. as you stated. I have a code reader from advanced auto and continally turned off the cel for about two-three months. The light began to bug me so I decided to fix the problem. I ordered all three cats from autoparts warehouse along with one new o2 sensor (bank 1 sensor 1). It is high up on the middle cat so I figured best to replace it now than half to figure out a way to get it off later.I also just went ahead and treated myself to a new christmas present and got the GReddy EVO 2 catback exhuast. The arrived in the mail and will be put on before the weekend. This was the cheapest fix in my opinion if you are set on turn off the light. I can let you know how it turns out by the weekend. BTW if you order from the same place make sure and order on the phone they will give you 10% off just for calling.

[Amosnorider]

Sounds like that might solve your problem. I would be very interested in knowing how it all turns out. Did your code turn itself off or did you reset it with the reader? I'm only getting p420 and it turns itself off while driving. Not sure what that means...

[dtuner]

Possible Causes:- Three way catalyst (Manifold)- Exhaust tube- Intake air leaks- Injectors- Injector leaks- Spark plug- Improper ignition timing

Check the plugs and injectors as those seem to be the more common issues with this code

He's right, all common issues for this code. Mainly check your vaccuum system because with most nissans 2000+ if a vaccuum leak occurs it can not only cause codes, but it can cause the engine to stutter and stall when it gets big enough. Emission codes are the trickiest because these computers read so many diffrent sensors to determine these codes.