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Jay, Nissan Technician
Category: Nissan
Satisfied Customers: 20233
Experience:  20+yrs experience with Nissan & Infiniti Trained & Certified.Currently still working for Dealer
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NISSAN FRONTIER: I have an ongoing po420 engine code on my

Resolved Question:

I have an ongoing po420 engine code on my 2002 Nissan Frontier(2.4). I' ve asked some of Just Answer's techs as to what the problem might be and followed the diagnostics as suggested. The most recent suggestion was to replace the cat converter. I was told that replacing the cat should take care of the problem 90% of the time. Well I replaced the cat to no avail and a unnecessary cost to me. I need futher diagnostics in this matter. If more information is necessary to help to help you in your diags I will be more than happy to supply you with what repairs that I have already made to the truck to try to solve this engine code problem. Thanks.
Submitted: 5 years ago.
Category: Nissan
Expert:  Jay replied 5 years ago.
Hello and thank you for using

Did you replace the Catt Converter with a Factory Catt or a After Market Catt?

Let me know, Thanks Jay!
Customer: replied 5 years ago.
I replaced my cat with an aftermarket cat. But let me say this. I removed the cat & inspected it before replacing it. There was no external damage & no clogged or burnt element. I've done my share of research about this code & it seems that this is a code that requires more than replacing the cat. I'd like to know why you asked me that question. The dealer wanted $900 for the cost of the cat & three hrs labor to replace it. It took me 15 minutes to remove it & an half hour to install the aftermarket cat. That would be a total of $1200. We are talking about a 2002 Frontier. Yes I went aftermarket.
Expert:  Jay replied 5 years ago.
The Material After Market Catts use doesn't converter the exhaust gases the same as the factory. The factory Catts use Platinum to convert the exhaust gases. The 02 sensors are sensitive to these gas conversions. Even though it may not be broken up on the out side, it could be in the center where the problem lies. In any case, since the converter is already in, and I do agree that it's cheaper to go after market. But they never work. So what I normally tell people who don't want to spend the 900 bucks on a new converter is just buy a rear 02 sensor spacer. This will pull the rear 02 sensor out of the exhaust stream so you won't get the P0420 code any more.

If you have any more questions on this, please feel free to ask. Thanks Jay!
Customer: replied 5 years ago.
Jay I like your theory. What thickness spacer are you talking about and will this get my mpgs back to what I'm used to. Will it also get rid of the sluggish sound from my exh when I shift to 5th gear? Meaning to say, when I drive with passengers they believe that I have an exh leak. I'm assuming that the spacer gets installed onto the rear 02 sensor(just before the catt). By the way, the rear 02 sensor that I installed was also aftermarket. I will reinstall the original sensor before adding the spacer. You have given me more diags about this code than my research has provided. I am a diesel tech so when you reply about what thickness spacer to use I would understand .001's.
Expert:  Jay replied 5 years ago.
The spacers come pre made from performance shops. See Image on what the spacer looks like.graphic

I can't say this will change the sound. It's possible the manifold maybe cracked. I can't hear the noise to say exactly. But the 02 sensor spacer will take care of the P0420 code. As for the Mpg, can't say until it's done to really see.

Thanks Jay!
Customer: replied 5 years ago.
DAMN! WHEN YOU SAID SPACER I WAS THINKING SPACER GSKT! So what you're doing is tricking the ECM. The sluggish exh sound is from the tail pipe. I checked the entire exh system for leaks. None found. Alright Jay, I like your answers and I will "ACCEPT". I think you spent enough time with me "for now" but I' like to keep in touch for another issue regarding a Maxima p/s pump noise. I will ask that at another time. I trust what you say and I'll let you know if this works. Thanks, Klaus.
Expert:  Jay replied 5 years ago.
You got it Klaus,

Thanks Jay!
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