Before I start, I put my car in limp mode the other night by accidentally shifting from 3rd to 2nd. That's in a different post if you care for all the (probably unimportant) details. But basically after that happened my CEL came on.

I'm throwing a P0420 code and my exhaust (GM Performance) is MUCH more quiet now. I've asked a few people and they told me that it is probably the catalytic converter. I know that this code could also pop up due to a busted hose somewhere, but the lack of noise from the exhaust is making me think that the cat is *probably* the issue here.


I have an appointment at my local stealership on Friday. After speaking with a tech on the phone he informed me that having the GMP exhaust would void the 8 year/80,00 mi warranty on the cat. I was polite and asked him to schedule me anyway and to please have IN WRITING why my GM certified exhaust would void my warranty. I did not mention my injen CIA but if it gets brought up I'll ask him to supply paperwork giving a reason why a CIA would affect a cat in ANY way, let a lone make it shut out.


Anyway, I need some advice on other possible reasons I would get a P0420 (catalytic efficiency below threshold).


As a side note, I am not going to drive it until I take it to the dealership on Thursday night, juuuuuust in case.

 

Do you have the stock air box? I would put it back on or they will say it skewed the MAF and caused the car to run rich/lean killing the CAT. Ive seen it happen a bunch of times here. They don't have a leg to stand on about the GMPP catback..... it says in there own parts book that it is authorized and doesn't affect the warranty at all.

 

I don't suppose they would have documentation stating the CIA would cause a failure in the cat? I don't imagine that they would and *by law* they have to prove that an aftermarket part caused another part to fail that would be covered under warranty otherwise.

 

Out of curiosity I went around the block tonight and got on it a bit in second to check the boost. I got up to 17 lbs. before I let off. I'm normally at 12 lbs. So p0420, quiet exhaust and more boost. Sounds like it has to be the cat, yes?

 

Update: Dropped it off at the dealership Thursday night to be looked at Friday. Got a call from the dealership just after I got off from work. They informed me that the problem was indeed the catalytic converter. They replaced it under warranty and informed me had they realized I had an injen cold air intake, they would not have done so (I have a decal on my rear window haha).


Anyway, all problems seem to have gone away and they also did the power steering motor recall as per my request.

 

awesome **** man. I was going to say it sounded like a clogged one to me. How'd they not notice you had a CAI? They had to of poped your hood.

 

Yeah they said it was falling apart haha. I was curious about that too. I was also curious as to how they got oil on my front bumper, upper grill, supercharger, battery box and engine. But it was all free and I made them clean my engine bay and exterior.