# 2005 PF WITH bank 1 o2 sensor p0420



## littlescrub (Dec 16, 2014)

Hi all I have a 2005 pathfinder that is showing bank 1 o2 sensor p0420. The pathfinder has 76000 on it. I have read on hear quite a bit. I have read a few thing that might be the cause like bad o2 sensor, but there are 2 which one would it be? Also that it may be the catalytic converter. Would some cleaner in the fuel be a good place to start? Any help would be appreciated. Thanks


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## IanH (Feb 11, 2003)

I have had this on my Lexus IS300.
It refers to the CAT efficiency. So check for exhaust leaks. If Ok it could be the downstream O2 or CAT itself.

But you can get rid of the code by using a spacer between the O2 and Pipe. These are called different things like "antifouler"

My post from then ........
P0430 p0420
I posted the link to where I purchased my Cat / O2 code P0430 fix on Ebay.

I just found out he doesn't sell on Ebay anymore but from a web site direct.

Shipped fast, good quality machining.

(Spacer $14.95 Each May 2011 shipping inc.)

http://www.bigdaddiesgarage.com/straight-cel-fix.html

www dot bigdaddiesgarage dot com

Good Luck.....


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## littlescrub (Dec 16, 2014)

Would taking away the o2 sensor with that sleeve affect gas mileage or anything else?


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## smj999smj (Jan 1, 2006)

Front or "pre-cat" O2 sensors are used by the ECM for fuel management whereas the rear or "post-cat" O2 sensors are only used for monitoring catalytic converter efficiency (meaning no affect on performance or driveability). Bank 1 is the right or passenger side of the vehicle (in the US). The O2 sensor spacer would be installed on the post-cat O2 sensor on that bank. This pulls the sensor slightly out of the exhaust stream and tricks the ECM by causing a false reading (the ECM looks at the rich to lean cycling frequency of the front and rear sensors and expects to see an approximate 2:1 frequency ratio for an efficiently working catalytic converter). Chances are if there are no leaks and no codes for anything else, and the engine is running well, you likely have an inefficient front catalytic converter on that bank. It's not uncommon on R51 Pathfinders. The only "snag" you might encounter with an O2 sensor spacer would depend on your states emissions inspection. Technically, using a spacer is considered tampering with a federally mandated emissions device. If you live in a state that enforces strict emissions testing, like California, it would fail inspection if seen by the inspector. In California and in states that enforce CARB emissions standards on CA emissions spec vehicles (if you have CA emissions), the only thing you can do is to replace the catalytic converter with a genuine Nissan unit or, if you can find one, a CARB certified aftermarket unit. In other most of the other states, aftermarket direct-fit converters are acceptable. Rockauto.com is usually a good place to pick up one; I recommend a reputable brand, like Bosal or Walker.


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## littlescrub (Dec 16, 2014)

I don't have any emission inspections here in Montana. The pathfinder is running good. So there is a good chance that it is a bad catalytic converter? If so and I trick the o2 sensor behind the front catalytic converter and this wont affect the truck in any way? Can it hurt to run with a bad or inefficient catalytic converter? For that spacer is there enough clearance for it?

Thank you so much for the help this is great!


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## smj999smj (Jan 1, 2006)

There should be enough clearance; if not, they even make elbow spacers. If the catalytic converter is inefficient, as opposed to being restrictive or clogged, it will not hurt anything (but the environment) by continuing to drive it. If it was restrictive or clogged, it would be a different story because it would create excessive back-pressure. "Inefficient" just means it's not breaking down the exhaust emissions as effectively as it should.


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