jwg2

I have a 2001 Z06 with a bone stock exhaust and engine tune that is regularly throwing P0420 codes (low efficiency cat bank 1).

Car has about 85k miles, including a lot of track miles, but is running well and doesn't appear to be down on power or any of the other symptoms you'd suspect with plugged cats or exhaust leaks. Three of the O2 sensors are original.

I am facing my day of reckoning with the Virginia emissions test and can't get this thing to stay code free long enough to get it past the man, so I have to finally deal with it. Search the forum here and just about all the P0420 threads are related to mods. The GM chassis manual is telling me that I should check for leaks and cat damage, then replace the cats. I am searching for CF tribal knowledge on this issue to see it I can trust the service manual or if there are other possible solutions to this.

ace147

Cracked cat. You were just unlucky and it died so soon. Some states require 70k mile emissions wrranty, but you are even past it. I have a spare set of cats waiting for the day my code throws (105k so far).

jwg2

thanks. I got 140k out of my last Vette's cat, was hoping this was cheap and simple.

jwg2

Does anyone have any vendor recommendations for replacing the cat? I want something that flows well, will last, and won't cause any emissions challenges.

92GA

My Vette had a damaged cat on it when I bought it. Had a hole on the inside. I replaced it with a Magnaflow, it only worked during the summer months here in IL. as soon as the weather cooled off it started throwing the codes again. I ended up buying a lower mileage H pipe off of a forum member and never had another problem. I'd put an ad up in the parts section to see what you may find. Even if you can only find one, it can be mig welded in place. The PO of my car had hit something in the road and dented the cat which broke the inside. Mine wouldn't throw a code as long as I was on the freeway but as soon as I drove it in town for about 10 miles it'd throw the code. Good luck.

RedZMonte

Magnaflow OBDII Spun cat 2.5"in/out. or find another stock H-pipe to swap. I have my stock exhaust but the shipping would be crazy to your location.

If you get a 2002+ Hpipe you will have 2 cats rather then 4..

S

jwg2

So got the car up in the air and began to investigate. There was no cat rattle, no damage to the O2 sensor wiring, but what I did discover was some burn through on the mating surface between the H-Pipe and the muffler, and consequently a small exhaust leak.

Never good, but could this leak well after the cat cause a P0420 code?

89vert

I would repair the leak before spending any money on a converter. My car was throwing a P0420 and I found a band clamp leaking. Fixed the leak cleared the code and it hasn't come back.

Dave02C5

gut the cats and get a custom tune.. end of story