Decision Making on P0420 and P0430 codes on Gen 2 2006 145k miles

[jskirwin]

Hi
I have had these codes for about 3 years now. I've somehow managed to pass inspection by clearing them using an ODB2 reader, but failed today. I'm tired of dealing with these codes and want to go about this the right way.

What decision making tree should be followed with these codes? I've scoured the Internet and while there is a lot of info on these codes on the Xterra, there is nothing that puts it together in a comprehensive manner that I can act upon.

My situation is the truck runs fine. Replaced spark plugs 2 years ago. Still have that timing chain whine which these trucks suffer from. I'm eying some cats at RockAuto, but before I spend the cash, I want to make sure I approach this problem in the proper way - the way an expert, honest mechanic would.

[muadeeb]

http://www.nicoclub.com/FSM/xterra/2...c.pdf#page=315
If you go to Nissan, they'll want to swap out the cats. Before you do that, since you have both codes, run an extra ground wire to the exhaust. If that doesn't clear it, my next step is to move the rear O2 sensor out of the exhaust using a couple of spark plug non-foulers, or a CEL eliminator; I've cleared a few p0420 codes using this method. To me, it's worth trying a few $10 fixes before shelling out $300 - $400 on a pair of cats.

[Tarditi]

FWIW - I replaced a bad cat myself... easy job. Used a magnaflo from Oreilly (best shipped price)

http://www.oreillyauto.com/site/c/se...rra&vi=1433008

Here's some background info for you if you're wondering about what to do with the codes:
http://www.nissanoffroad.net/message...?topic=5445.15
http://www.thenewx.org/forum/showthr...ighlight=P0430
http://www.thenewx.org/forum/showthr...ighlight=P0430
http://engine-codes.com/make/nissan

[jskirwin]

Thanks for the help guys. I'm surprised to be replacing cats on a vehicle. This isn't the first one I've driven over 125K - I've got a few others under my belt although this is my first truck.

[muddy]

Im suggesting you go ahead and replace the cats asap. Im a certified nissan tech and ive seen lots of frontiers and xterras and pathfinder cats break apart/crack throwing the code.. worst case scenario ive seen is pieces of the cat sucked back into the motor on decel.... you can imagine what happens then.

a lot of the local 4x4 guys break cats internally when they submerge them off road. imagine the glowing hot cat getting soaked in water. contraction causes them to break.