DTC Codes: P0420 and P0430 - Nissan Forum
A33 2000-2003 Chassis 2000-2003 Maxima

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post #1 of 6 Old Nov 22nd, 2005, 05:50 PM Thread Starter
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DTC Codes: P0420 and P0430

Hello All...

New to the forum.....

I have a question regarding my 2001 Maxima SE. It has 162,000 almost trouble free miles.

My check engine light is on, and I am getting Codes: P0420 and P0430, Catalyst Efficiency below Threshold Banks 1&2

The dealer says I have to replace both catalytic converters and all FOUR O2 sensors. That runs almost $2800 total...

I really don't think its the catalytic converter because she's running strong as ever and I have not smelled the "sulfur" smell as i've read from the other posts.

Anyone might know how I can begin to trouble shoot this??

Much Appreciated!

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post #2 of 6 Old Nov 22nd, 2005, 06:14 PM
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Wow, is the dealer including a lube job with that?

More likely it's just o2 sensors that are getting old. Should be $100-150 a pop if you use genuine Nissan replacements. $15 for a 22mm open-end wrench and $3 for some anti-seize compound... then do it yourself.
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post #3 of 6 Old Nov 22nd, 2005, 09:48 PM
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I agree with Brian.... do the O2s yourself and see what happens.

Use this the diagrams in this TSB as a guide:


Additionally, the FSM lists some other possible causes that you can check:

Exhaust tube
Intake air leaks
Injector leaks
Spark plug
Improper ignition timing
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post #4 of 6 Old Nov 22nd, 2005, 10:11 PM
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Just to add one more thing, the 420 and 430 codes are for both pre-cats. If they go bad, you won't necessarily smell anything because the main cat will still be able to take care of that.

I'm beginning to doubt the O2 sensor replacement as a fix, but I know for sure that an O2 simulator to trick the ECU will work as a quick (and cheaper) alternative to replacing the pre-cats. You can read more about em at www.o2sim.com.

Alternatively, you could get aftermarket headers and do away with the pre-cats altogether, it'll be cheaper than getting new pre-cats and you'll get about an extra 20 whp to play with.
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post #5 of 6 Old Nov 14th, 2007, 06:12 AM
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be careful, replaced to downstream o2 sensors and the light came back. the quality of nissan is deteriorating. i have a feeling the cats are bad. but in any case even if you have to replace the cats the o2 sensors first this is the first time that i will have to change the converters. 95 % the o2's worked
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post #6 of 6 Old Dec 1st, 2007, 09:24 PM
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hello, i am wondering, i have changed both downstream oxygen sensors, in 2 different nissans, 1 maxima and 1 sentr. the one in the sentra somebody changed the converters and the upstresn o2 sensoer. i was wondering on both nissans, i only saw the engine temperture get to 176 degrees farenhieght. i have not seen the cars again but my next step is change the thermostat and see if i can get to 190 or higher. i am worndering if the car is running a slight rich from the cooler temperture. if you change the thermostat and the problem solve please post it
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