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2000 Infiniti I30 code P0430: which catalytic converter?

I’ve got about 135k miles on my 2000 I30. The SES light is on; AutoZone checked the code for me: it’s P0430: “Catalyst system efficiency below threshold- Bank 2” (and no others). My mechanic says the catalytic converter needs to be replaced. He’s replaced some O2 sensors before; apparently he knows they’re OK; I should have asked (but didn’t) whether he actually troubleshot the O2 sensors, but I assume he did, because he’s done it before. The dealer says it’ll be $1100, my mechanic says $650, and my muffler guy says $400. The only problem with the muffler guy is that he doesn’t know which one is Bank 2.

My questions are: given the info above, is it clear that the catalytic converter does need to be replaced? What would happen if I don’t replace it? (I’m in Alabama: the air is clear; there’s no emissions testing. I want to know what would happen to the car.) And finally, which catalytic converter is Bank 2: the one next to the radiator, next to the firewall, or underneath the passenger compartment?


I don’t think that the codes P0420 or P0430 (they are both for the catalyst efficiency below threshold 420 is for bank 1 and 430 bank 2) are very clear cut deals. I got a 420 on my Camry a couple months ago all I did was take the car out for a 3 hour cruise at 65MPH plus with out using overdrive and haven’t had the code since. It could conceivably even be a lazy O2 sensor. But I do know the bank 1&2 answer, Bank 1 is the side with cyls. 1,3,5 Bank 2 is cyls. 2,4,6