Camaro book says this is "cat converter left bank". SES went off after awhile but now is back on. What could this be? A muffler shop checked it and said the cats were fine. Has been no noticeable performance hit. Any suggestions greatly appreciated.

2002 Z28
85mm MAF
K&N Filter
SLP Loud Mouth
RAM cut out

 

It's most likely a bad driver's side cat - covered under the federal emissions warranty for 8yrs/80K. Do a search here for "P0420" it's a very common problem. Welcome to the board.

 

I had the same problem around 55K. Does your exhaust smell like rotten eggs?

I took it to the GM dealership where I bought it and they replaced both cats. under warranty.

 

Thanks for the responses! Heck ya exactly...rotten eggs!! I'm marching to the dealer right now!

 

Man the dealer gave me a rash of crap! They didn't want to warranty it because I had modified the exhaust. But I only put on Loud Mouth tail pipes.

 

Did they replace it? My buddy had his replaced w/GMMG and cutout installed. If not try another dealer - even a catback shouldn't be a problem, Corsa catbacks are "GM approved."

 

I've had that code pop up twice with my car now (~44,000 miles on the clock). Funny enough, I had a catalytic go bad about a month ago (I honestly don't even know which side?! ) but the code came in about a month or two before getting the new cat, and now a month later!

 

That's BS. Tell that service advisor to take a closer look at your car and see the factory exhaust on there. If you ONLY have aftermarket tips on there that shouldn't void anything.

Better not add anything else like pinstripes or that dealer won't touch your car anymore.

 

Well they finally gave in after 2 hrs of debating. They said they would go ahead and replace both of the cats but only because they were "bolted in." Had the tubes been welded...no way they would do it. Guy at muffler shop advised me to get some kind of bolt in pipes to get rid of the cats and bolt the cats back in come inspection time. Any tips on this?

 

If you do that then you'll need 2 O2 simulators for the rear O2 sensors and you'll be good to go.

 

Get them changed first and then if u want, go for the offroad pipes but not sure if u'll have the problem of rasp since u have the SLP LM even though u don't have LT's....not sure. That is BS kinda though, SLP should be approved and not void the warranty since they work with chevy/GM. I had a rattle by the gas tank heat shields a couple weeks after i installed my GMMG. When i took it to the dealership the guy asked me what was wrong, i told him i think it's the gas tank heat shield. So i started it up and he made a joke about not fixing it under warranty but he didn't care. Surely enough it was my GMMG rubbing on a heat shield and they fixed it for me at no charge. Another time before that i kinda f'ed up my car and my passenger side cat started to oxidize and after a month my ses light went on cuz it made a hole in the cat. I took it to the dealership thinkin i would have to pay for it to fix it since i'm sure they could tell i hit something, but they fixed it free of charge.