# 2006 altima 2.5 with code (p0420)



## 1cln_sdime (Oct 29, 2013)

Just wondering if the 2006 had the same pre cat issue as the earlier modles? This car uses a qt of oil about every 3 to 4k so it isn't to bad. Just wondering if I need to gut the cat when I have the front end apart (had a lil wreck).I called a local trusted mechanic he is family he said he doesn't think its the pre cat and said it sounds more like a evap issue aka vac leak of some sort? Just looking for some more opinions. Thanks for any help I can get.


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## smj999smj (Jan 1, 2006)

The 02-04 models were the primary one involved in oil burning issues due to the converter breaking down, which was, according to Nissan, due to the ECM programming. That said, I don't see how an evaporative emissions system, which is used to store fuel tank vapors, nor a vacuum leaks, would cause your engine to burn oil. Gutting the catalytic converters will not fix the P0420 issue; that would require replacing the catalytic converter as it has become inefficient. While removed, you can then inspect the inlet side of the catalyst media for signs of burnt oil.


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## 1cln_sdime (Oct 29, 2013)

I live in Kentucky and have no inspection to pass and purly trying to save the engine. In you opinion is that code from the cat beginning to break down, the car has 125k on it. If it is starting to break down im either going to gut the cat or put a header on the car as long as I can do so without making it any louder. I just can justify spending 300 on a part that does nothing but choke the exhaust system. If you don't think it is the cat where do I need to look? Thanks for the help.


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## smj999smj (Jan 1, 2006)

P0420 is an efficiency code...which means it is not breaking down the emissions efficiently and not necessarily means the catalyst substrate is falling apart. The ECM checks efficiency by comparing the rich/lean cycling of the front O2 sensor to that of the rear O2 sensor. The rear sensor cycling frequency should be about half of that of the front sensor. If the cycling frequencies are close to being the same, it will trip a catalytic efficiency code (P0420). If you got the converter or install a header, you will still not be breaking down the exhaust emissions efficiently, so the code will continue to reset until you install a working converter or do something to trick the system, like installing rear O2 sensor spacers (which sometime work and sometimes don't).


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## rogoman (Dec 16, 2004)

1cln_sdime said:


> I live in Kentucky and have no inspection to pass and purly trying to save the engine. In you opinion is that code from the cat beginning to break down, the car has 125k on it. If it is starting to break down im either going to gut the cat or put a header on the car as long as I can do so without making it any louder. I just can justify spending 300 on a part that does nothing but choke the exhaust system. If you don't think it is the cat where do I need to look? Thanks for the help.


If you plan to install a header, here are some web sites that have a solution for eliminating the P0420 code:

SINGLE MIL Oxygen Sensor Simulator, MIL-Eliminators.com

HowTo: Remove Notorious P0420 Code for less than a buck!!

Don't know how well these solutions work, but it's worth at least looking at them.


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## 1cln_sdime (Oct 29, 2013)

Just a little update, I checked for vac leaks and there are none. I found that the ambient air temp sensor wire had been cut in a little fender bender I had about a year ago. So I fixed that wire and poured 2 bottles of chevron fuel system cleaner in and cleared the ses light. I drove for about 40 miles todays with no ses light and also my car had been getting terrible fuel milage on getting about 20 mpg but tonight I was getting 29-30. So at this point the sensor and the fuel system cleaner seems to have it fixed. Im still going to pull the exhaust manifold and check if its coming apart or getting clogged. There has to be a reason im losing 1qt between oil changes.


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## smj999smj (Jan 1, 2006)

Do a compression and cylinder leakdown test.


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## 1cln_sdime (Oct 29, 2013)

Im going to this weekend ill let u know what I find out.


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