# 04 sentra 1.8L Catalytic Converter help



## AGodlyCanuck (Sep 6, 2015)

So, i am new here and i have been looking for reliable forums to help me with my issue. Right now my main issue is that i have a check engine light on and error code po420 an po420pp.

So i looked under my car for holes and leaks and it all looks pretty solid. Just a bracket had broken off at the weak welds. As i have also noticed a mild luggin feeling. Now this could be due to a sensor causing the engine to think it needs this and "adjusts" or it could be a the cat. However this car has 222,000kms and the cat is factory. So i am confused as to which i need.

Could anyone point me to the right direction? I would need one that is attacthed to the manifold, however it looks like there are 2 other cats on the exhaust. if so id just want to remove those completely as i will not be needing or getting an inspection. I went to the parts store ( Lordco, Napa )
No one seemed to know for sure. ( need to know the parts for Lordco because i get 50% off)

Sorry if this is a lot of information. but its a frustrating issue.:|


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## smj999smj (Jan 1, 2006)

A P0420 is a catalyst efficiency code. Catalyst efficiency is determined by the ECM by looking at the rich~lean cycling frequency of the front, or upstream, oxygen or air/fuel sensor(s) and comparing them to the rear, or downstream, oxygen sensor(s). Only the catalytic converter(s) between the upstream and downstream sensor(s) is/are monitored by the ECM for efficiency. It is rare for a rear catalytic converter to go bad because the upstream converter sorta acts like a filter to the rear converter. Ideally, under specific conditions, the ECM wants to see a 2:1 ratio between the front and rear sensors. The front oxygen or air/fuel ratio sensor is used by the ECM to help it determine whether it needs to richen or lean out the fuel mixture via fuel injection pulse duration. The rear oxygen sensor has no affect on fuel management and is only used for monitoring. Just because a catalytic converter is inefficient, doesn't necessarily means it is restricted or block; it means it is not breaking down the exhaust emissions the way it is supposed to do. 
Most of the time when a P0420 or P0430 code is triggered, it is usually due to an inefficient converter (the one located between the front and rear sensors) and it needs to be replaced. The only way to be certain is to follow the diagnostic procedure listed in the service manual for the specific trouble code triggered. Removing a catalytic converter after the rear sensor will not affect fuel management nor will it cause a code to trigger and you may experience slightly better performance; in the USA, tampering with or disabling any catalytic converter or emission device is technically illegal, but it sounds like you are outside of the USA so go by your country's emission laws.


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## AGodlyCanuck (Sep 6, 2015)

Yeah, in Canada what will happen is they just test the emissions and you fail you get a fix it ticket (fix it within a month or be fined) or be denied registration and don't pass inspection.

But because I live in an area of Canada without inspections. Its "legal".


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