# Nissan Code P0420 Review



## moose (Dec 14, 2004)

My 2000 Maxima has had Code P0420 reported when taken to the dealer with the service engine light on. The dealer stated I needed the front cat. and an O2 sensor($1200.00 est). I had them reprogram the light off. I took the car to a PA inspection station and the car passed the emissions test easily. Shortly after that the engine light came on again, I went to another Nisan dealer and the same P0420 came up. When I told him the car passed the emissions test he couldn't explain why I needed a new cat. and O2 sensor. One of the technicians said there was a Nissan net bulletin that states the codes may be overly sensitive. Now I have the light staying on and am not sure that I really need to spend the $1200.00. Any suggestions would be greatly appreciated.( I have 82,000 miles on the car, so there is no warranty provision,)


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## MilkSeR (Dec 6, 2004)

WElcome to NF.com, i d post that in the maxima section of the site, a lot of info there.

http://www.nissanforums.com/forumdisplay.php?f=10


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## LatinMax (Feb 23, 2003)

More information is needed.

Do you have after market exhaust, Y-pipe, CAT, B-pipe...anything.
I get the same code for not having a CAT.
Reply and I will have more answers.


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## moose (Dec 14, 2004)

*Reply to P0420*



LatinMax said:


> More information is needed.
> 
> Do you have after market exhaust, Y-pipe, CAT, B-pipe...anything.
> I get the same code for not having a CAT.
> Reply and I will have more answers.



No special exhaust, everything is stock. Can you get your car inspected without a CAT?

Regards,

Moose


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## LatinMax (Feb 23, 2003)

moose said:


> No special exhaust, everything is stock. Can you get your car inspected without a CAT?
> 
> Regards,
> 
> Moose


No, you can't if they do emissions. It will fail.


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## brianw (Feb 25, 2004)

At 82k, checking o2 sensor functionality might be a good idea. Check the FSM, it should have instructions on how to do that with a multimeter.

New O2 sensors are a hundred bucks each, give or take.


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## pathfound1 (Apr 8, 2004)

*i think i had a similar problem*



moose said:


> My 2000 Maxima has had Code P0420 reported when taken to the dealer with the service engine light on. The dealer stated I needed the front cat. and an O2 sensor($1200.00 est). I had them reprogram the light off. I took the car to a PA inspection station and the car passed the emissions test easily. Shortly after that the engine light came on again, I went to another Nisan dealer and the same P0420 came up. When I told him the car passed the emissions test he couldn't explain why I needed a new cat. and O2 sensor. One of the technicians said there was a Nissan net bulletin that states the codes may be overly sensitive. Now I have the light staying on and am not sure that I really need to spend the $1200.00. Any suggestions would be greatly appreciated.( I have 82,000 miles on the car, so there is no warranty provision,)



Well i had a problem with my engine light coming out and my mechanic said it was the catalytic converter. So i called Nissan headquarters and told them about my problem and they told me that i should take it to a nissan dealership and said that the catalytic converter has warranty of up to 80,000
miles...check ur manual (it should say it) but anyway i took it to nissan and they told me that it was not in fact my converter but my ecm ( engine control module). recently my light came on and in 2-3 weeks it turned off by itself..i dont know what it could be but it could have been the fuel cap, and how it was twisted on right. so maybe check that or go to ur mechanic turn the check engine light off and see if it comes back on. if it comes back on it usually comes back on in like 2-3 weeks.


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## NoKTournAL (Feb 11, 2003)

moose said:


> My 2000 Maxima has had Code P0420 reported when taken to the dealer with the service engine light on. The dealer stated I needed the front cat. and an O2 sensor($1200.00 est). I had them reprogram the light off. I took the car to a PA inspection station and the car passed the emissions test easily. Shortly after that the engine light came on again, I went to another Nisan dealer and the same P0420 came up. When I told him the car passed the emissions test he couldn't explain why I needed a new cat. and O2 sensor. One of the technicians said there was a Nissan net bulletin that states the codes may be overly sensitive. Now I have the light staying on and am not sure that I really need to spend the $1200.00. Any suggestions would be greatly appreciated.( I have 82,000 miles on the car, so there is no warranty provision,)


If the new programming was done and the P0420 code came back you need the front pipe pre cat, I have 2 left over from various CA/NLEV-FED Spec conversions I've done on a few of my friends Maximas, I know the front pipe cats are still good cause they were on for about 20K before a YPipe was added to their exhausts, PM me if you need one, if you want to go the extra step and do a full fed spec conversion PM me and I can tell you in detail whats needed. If the P0430 code came up I also have the front manifold precats as well with less than 40K on it.


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## bguild (Jan 6, 2005)

I'd just like to add that I believe $1200 for a cat and O2 sensor is unacceptable. That must be like a 1000% markup. wow.


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## schwendawg (Jan 6, 2005)

My mechanic found this code on my '01 Maxima as well, however he also found a Technical Service Bulliten that said the dealer would be able to reprogram the ECM, and that this should solve the problem as opposed to replacing the catalytic conv. The dealer I'm taking it to said this would be covered under warranty and that there would be no charge. I have the appt tomorrow, hopefully this will clear it up.


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## chucho (Jan 7, 2005)

Hi ima nissan tech, i have found that nissan is very strict with there emissions
i get alot of maximas with those codes. most the time we just reprogram the 
ecm covered under warranty up to 80k miles. If its already been programmed
then we have to replace the front tube and o2 which is normally only covered under the 36k miles, unless you have extended warranty.


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## NoKTournAL (Feb 11, 2003)

chucho said:


> Hi ima nissan tech, i have found that nissan is very strict with there emissions
> i get alot of maximas with those codes. most the time we just reprogram the
> ecm covered under warranty up to 80k miles. If its already been programmed
> then we have to replace the front tube and o2 which is normally only covered under the 36k miles, unless you have extended warranty.


Front pipe w/ precat is covered under P0420 bulletin

7/70K I believe it was
same for exhaust manifold/ pre cat on front bank

pnc listed in warranty book 

obviously run DCS to verify emissions 

I think the 01-03 Pathfinder front tubes are the ones you are talking about before they came out with the repair kit, thats 3yr/36K


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## schwendawg (Jan 6, 2005)

schwendawg said:


> My mechanic found this code on my '01 Maxima as well, however he also found a Technical Service Bulliten that said the dealer would be able to reprogram the ECM, and that this should solve the problem as opposed to replacing the catalytic conv. The dealer I'm taking it to said this would be covered under warranty and that there would be no charge. I have the appt tomorrow, hopefully this will clear it up.


Picked the car up Friday. The ECM was reprogrammed (Seemingly to take the stringent emissions standards that chucho speaks of away) and they also replaced the O2 sensor. Unfortunately, I picked it up after close, so I couldn't see which one. The O2 sensor was covered by my ext'd warranty, and Nissan covered the ECM reprog as the car only has 39k on it. Obviously enough, if you have someone tell you that a new catalytic converter is necessary, be sure that they've checked this, and take it to a dealer to have the reprog done for free. A quick and easy way to alleviate the sticker shock that comes with that kind of work.


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