# p0420 code help



## nissanpark1 (Jun 18, 2008)

My 2000 nissan sentra GXE "service engine soon" light turned on in january(69720 mile). I checked it up by dealer. They told me some o2 sensor was wrong.

here is the report.
P0420 Tw catalyst system B2. Catalytic convertor function failure.
Front and rear o2 sensors for B1. Rear o2 sensor b1 response is like front o2 sensor b1 reading. No function through catalytic convertor. Correction on cause system is bank1 not bank 2.

can you help me figure out which sensor is wrong and how to replace it?

thanks


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## saint0421 (Sep 24, 2006)

nissanpark1 said:


> My 2000 nissan sentra GXE "service engine soon" light turned on in january(69720 mile). I checked it up by dealer. They told me some o2 sensor was wrong.
> 
> here is the report.
> P0420 Tw catalyst system B2. Catalytic convertor function failure.
> ...


Um, it's not a o2 sensor failure. You're cat convertor went to poop. When your second o2 sensor reads the same as your first o2 sensor it means your cat is gone.


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## nissanpark1 (Jun 18, 2008)

I went to the send dealer, they said it is Catalytic convertor failure, it is still under warranty, they replaced it for free. it was covered for 8 years and 80000 miles nationly.
so the first dealer tried to rip me off.


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## saint0421 (Sep 24, 2006)

nissanpark1 said:


> I went to the send dealer, they said it is Catalytic convertor failure, it is still under warranty, they replaced it for free. it was covered for 8 years and 80000 miles nationly.
> so the first dealer tried to rip me off.


Glad you asked around first. You could report the first dealer to BBB. Maybe get something out of it. Them trying to rip you off is just wrong.


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## metro273 (Sep 16, 2005)

That PO420 is VERY common on the 2.5 and 1.8 engines...


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