# P0420 code - there are two cats, correct?



## Superbaldguy (Oct 30, 2005)

I have been getting the occasional 0420 code which indicates a bad or dying catalytic converter. Is this most likely the manifold one? I thought there was one at the back of the exhaust system. Has anyone tried to use a cleaner to get rid of some of the gunk in the honeycombs?


----------



## SPEEDO (Jun 9, 2003)

It will be the one off of the manifold or the exhaust manifold itself, depending on the engine....


----------



## Superbaldguy (Oct 30, 2005)

I have the 1.8L - is there a way to test to see which cat is the issue?


----------



## smj999smj (Jan 1, 2006)

The catalytic converter between the front and rear O2 sensors will be the one that is bad if you get a "Three way catalyst" DTC (ie P0420 or P0430). The differeance between the P0420 and P0430 is they are on opposite banks of the exhaust system.


----------



## Superbaldguy (Oct 30, 2005)

So this is the manifold cat that is dodgy. I suspected that. I had one replaced under warranty around 145,000 kms. I have a couple choices - find one from a salvaged Sentra or try some of that Catcleaner. Since my car has 384,000 kms on the odometer, I really am at the point where spending money on a brand-new one is not feasible.

Thanks for all the input this far.


----------



## smj999smj (Jan 1, 2006)

It's illegal for salvage yards to sell used catalytic converters.


----------



## Recian (Sep 30, 2008)

Like was mentioned used cats are illegal. I think it was some scam to allow yards to scrap all the converter metal to sell to the suplier. Also nissan cats usually dont fail for clogs they deteriorate and come apart. Cleaning it wont help. There are 2 cats on that car both are on the manifold each side monitored by 2 02's on top 2 02's on bottom. Best bet is to buy a new one from the dealer. Alot of shops wont even try to weld cats into a manifold.


----------

