Dustin's Z

I have a 2000 z28 it is throwing 2 codes , p0420 catalyst efficiency below threshold (bank 1). I replaced the 2 oyxgen senors before the catalyst. It seem to make it run better but i dont know wat else it could be???

2001NBMZ28

P0420 99% of the time is a bad drivers side cat. Precat 02's don't have anything to do with it, the rear 02 on that side monitors them. If you're under 80K cats are covered under the federal emissions warranty. You can try swapping the rear 02's side to side and see if the code changes, but most likely it's the cat.

Dustin's Z

should i go ahead and fix the 02 senors, or should i go with the 02 simulators and get rid of the cats??

2001NBMZ28

If you're over 80K and the cat is bad I'd either gut them both and go with sims or have the codes turned off permanently. Of course you could replace the cat also. Don't have emissions here in Florida, your area might be different. JMO