Disclaimer:
This is bad for the environment........ Do what nissan says and replaced Both Catalytic converter to the tune of over $2000...
Oh and if you break anything doing this cheaper fix it's not my fault. What worked for me may not work for you.

P420??? P430??????????????
Catalyst system efficiency below threshhold Bank 1 or 2...............right????????????????????

I have a crazy fix for this code but first alittle background.

I started throwing P430 which is the same code as you but for Bank 2 side. I played with it for months resetting the code and paying attention to when it would come back on. I can watch the O2 sensors with my scan tool and could tell from the freeze frame of the code it was only tripping the code because the efficiency was just barely out of tolerance every now and then. (HELL IT COULD BE BECAUSE OF THE 10% ETHANOL CRAP IN THE FUEL NOW!) Now sometimes I can drive a month and sometimes only a few days before the light would come on. Which basically means my Catalytic converters were only bad from an environment stand point and just barely. There's not anything really wrong with the pathfinder.

N-E-ways.... The BIG dollar fix is to replace back Catalytic converters which would cost quite a bit. Or trick the ECU into thinking that everything was just fine.
I choice the cheaper route. Only cost my $10 LOLOLOLOLOLOLOLOL

Here's what you need.


Buy a package of non foulers, Start small and slowly enlarge the hole all the way up to a 1/2" drill bit.

Now pull the rear O2 sensors and install the non-fouler onto the O2 sensor and then screw it back into the exhaust. I did it to both sides so they are the same. Everything only took my about 30 minutes.


Now the theory behind it is the O2 sensor is now pulled out of the direct stream of exhaust gases. Because of this it's seeing less of a sample of exhaust gases. Rear O2 sensors are not used to adjust air/fuel ratios. It's there for government emissions measuring. Now that it's seeing less of the bad stuff it's sending that signal to the ECU and the ECU likes it.

So far I've driven 8000 miles with this fix and haven't had a single problem and there's been NO LIGHT ON.
Fuel mileage didn't change AT ALL.

It worked for me!

Yep

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Nico Exclusive?

this trick has been around for YEARS.

Would this mess up your air/fuel ratio (if used on the pre-cat sensors)?

it would totally jack up your AFR if you use it on the upstream sensors. if you have a bad upstream O2S, it should be replaced ASAP.

the computer will accommodate a bad upstream O2S by using the downstream O2S to calculate AFR and adjust fuel mixture to stoichiometric, but it's not very precise and your fuel economy will surely suffer.

never use a simulator or spark plug non fouler on an upstream (pre-cat) oxygen sensor.

alexf20c wrote:it would totally jack up your AFR if you use it on the upstream sensors. if you have a bad upstream O2S, it should be replaced ASAP.

the computer will accommodate a bad upstream O2S by using the downstream O2S to calculate AFR and adjust fuel mixture to stoichiometric, but it's not very precise and your fuel economy will surely suffer.

never use a simulator or spark plug non fouler on an upstream (pre-cat) oxygen sensor.

^^^^^^^^^^^^^^^
I agree 100% Do not do this to the upstream O2 sensors.

amaff wrote:Yep

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I'm sure the trick has been around for a long time. When I was having this problem I searched the internet for hours and never found a solution to codes P420 or P430. I was getting super frustrated because nissan told me it would be $2600 to fix it. Lucky for me my brother suggested this idea to me and it worked.
The Main purpose for this thread is now when something googles P420 or P430 and pathfinder it'll bring them to this thread and they now will have another option to try and fix it.

k so i have everything to do this little mod but i went under my car and have no idea where to look for my downstream o2 sensor...... could you guys help me out? it's inline with all my exhaust piping? i have to take off some piping to get to it or am i looking in the wrong place? trying to do this before the sun goes down here so if you have any ideas then shoot thanks

FOUND IT!!!! just had to look around for a while...............

Body80.... I've been working on cars, infinity since y first q45 I 1992.

You saved my life wit the spark plug fowling thing. I did buy some new back 02 sensors and I took a lot of time matching wires and soldering each connection. I would get code 420, 430. 57 and everybody wanted to put I pn two new catalytic converters. About 3k and I said hell no and built the shrouds around the sensor. No problem and I reset the ODBII sensor and the are gone! You could drive about 5 minutes and thr CEL would pop on...I'd reset abpnd I read a bunch.

I'm 67 years olds fart that had to quit work because of cancer. So instead of 3k I spent 11.00 at Harbor Freight for two sizes of sensor sockets NAND 50.00 vow two sensors from a company that is one that....this is all we build.

I'm a ME and I know so much old stuff it's amazing. I started with Ford flathead all the way up to 500hP big block stuff.

You learn something new everyday!

Thanks

Bill. golfez

This little 290 horse will scoot.

This would be wonderful, but who can I get to do it? I mean, is it legal (I'm in Virginia)? I don't want to offend my shop guy by asking him to do something wrong. On the other hand, my engine light has been on and off (mostly on) for the last year and they can't isolate it. BTW, they replaced all four O2 sensors when the CEL problem initially appeared.

The situation became critical two days ago when my 2002 Pathy started misfiring and my CEL FLASHING! So, I had to take it to the nearest shop instead of to my regular guy 18 miles away. The current shop ran a diagnostic and pulled multiple codes including a cylinder 4 misfire and the dreaded 420 and 430. But they didn't really believe the cats were clogged (just probably inefficient), so they tried a simpler, cheaper fix first: replacement of ignition coil #4 (left side). They also replaced the corresponding spark plug (total about $370, including diagnostic fee). They drove it twice and said it ran great, but when I picked it up in the evening it was back to the same misfiring, possibly a bit worse. I keep asking about the catalytic converters because the car has 226k miles on it with original engine and cats, but they're not convinced it's worth spending the $2400 on them right now b/c it might not solve the problem. They are suggesting a $350 replacement of the fuel injector O-ring (2-3 hours labor, cheap part).They said there was some kind of tech alert about it. I'm skeptical b/c it might not fix it AND I might STILL have to shell out $2400 for new cats after this. If I go with cats, I'd really prefer if my regular garage did the work since they have the O2S history and because they are a small local shop of great guys that would probably only charge me $1800-2000(?).

I'm really counting on you all to give me some guidance here. Please respond in plain language because I am not very knowledgeable about automotive terminology. Thank you! --Dawn

P.S. two more tidbits of info in case it might matter...
1. Same time last year, I used this "nearer" shop for another last minute emergency prior to traveling for Thanksgiving and they did a tune up along with a valve cover replacement--a whole 'nother story since they used the wrong one initially, come to find out Nissan redesigned it. I only drove 900 miles on the WRONG one! They did their best to make it right, but I now read that many folks have had problems with the valve cover issue clogging their cats... Immediately after that fix, I dropped from 16 mpg to 14. Throughout this year it has waivered between 13.5 and 15.5 but the garage says it's not related. But it was clearly a before:after case.
2. Right before the car started acting up two days ago, we filled up the gas tank. Could bad gas have set off a serious of unfortunate events?