I have an 07 Cobalt SS/SC. It has a AEM intake, a DC Sports exhaust and a 3.0 inch pulley and NGK 1 step colder spark plugs. I was driving on the highway and downshifted into 4th to pass a truck and thats when all hell broke loose. The engine stayed on but the gas petal got no response and the tach dropped to 0. I was coasting on the shoulder and would restart the car and have it turn on but the gas petal and tach got no response. I sat on the side of the road for 5 minutes and the car was able to drive again but the check engine light was on. Next day at autozone i get the codes checked and it said something about the crankshaft post sensor and that the catalytic efficiency is below threshold. Me and my friend took off my exhaust and the cat is toast. Pieces of it were strewn all the alone the exhaust piping.. The dealership has the car and is saying that they might not cover the CAT because of my exhaust which is the same piping size as stock and because my pulley changed the boost on the car and that supposedly could of messed up the sensor and the cat. I understand once you mod your basically screwed but if anybody could hand up any advice that would help support my case that these mods didnt destroy the sensor or the cat. Im 20 and paying for the balt by myself and going to school so if I dont have to pay for a new cat it would really help me out. Thanks

 

I don't see how they can blame it on the exhaust. It is just a cat-back correct? So the exhaust is already through the cat once it gets to your aftermarket exhaust... Now if you had a header and downpipe I can see they trying to pull that. They could point to your pulley yes. Even though the stage 2 kit has the same size pulley stage 2 is warrantied where your same size 3 incher isnt.

 

Yea what can i do about them blaming the pulley?

 

Not much really, they have decent reason to believe that a pully would change the way the car runs, which could no doubt have messed up the sensor and cat.
this might have happened without your mods, who knows, but they see mods, and mods that could directly have caused the problem.
that = big trouble.

You went aftermarket instead of going GMPP, this is the result.
If you wanted warranty you shouldnt have let them have it with those parts on there.
or should have saved up for stage kits

 

the same thing happened to me once...same condition...i was in GA running an RSX on the freeway, I was at like 4.5k in fifth gear...and had to downshift for some reason to fourth...well it ran me up to like 5.5k which was fine and all but then my motor lost power and my DIC said "engine pwr reduced"...I pulled off the road (well coasted off) shut the ignition off...and waited 5 minutes...then it started up fine and i drove it all the way back to morth carolina...this has only happended once...i got to work the next day and I pulled the CEL codes and I had similar codes so I asked my top tech to help with it...what he and I came up with was that when I down shifted and put my foot back in it...the PCM commanded more fuel and and air...and my MAF didnt change the signal fast enough which either ran me rich or lean can't remember but thats what threw what casued the oxygen sensors to go crazy hence the false cat. efficiency code...there are bullitens about a PCM reprogram for an Engine Power Reduced and the Cat. Eff. codes...I would tell the local Chevy that you know theres a related bulliten..and get them to reprogram the PCM.......I would tell ya the bulliten number but I'm between dealerships right now and have no access to Service Information or to GM Dealerworld......P.S. Cat.s due go out but unless you have very high mileage its unlikely

 

Why dont you just take off the downpipe and gut the cat. Wait a while and you will be able to buy a used Dp of someone on here. People sell them all the time. Gutting the cat takes like five minutes. Its super easy.

 

better find HP tuner, gunna need to do post 02 delete

 

You could take them to court to make them prove that your mods did the damage. The Magnuson Moss Warranty Act (sorry for the incorrect spelling)states that they have to prove that your modifications did the damage to deny coverage. However, if they can prove that the damage was caused by your mods you will have wasted time in arbitration and money. Just some thoughts.

 

when you guys downshift do you clutch, downshift, unclutch... or clutch, downshift, rev, unclutch??

 

i go with the rev match...i'm no gearhead but it seems like its better for the car

 

it is...

as for the "they have to prove the pulley was the downfall" that is pretty simple

 

I don't think you have much of a court case if they deny your warranty work for the cat and sensor . Was your car tuned for the 3in pulley? are you running stock injectors?

 

yea, but i'd bet GM has better lawyers than the average person can afford

 

No need for good lawyers when dealing with a clear cut warranty act problem, the law is on your side. Courts tipically don't like dealers trying to deny coverage for something not related to the problem. GM has to prove that the damages were caused by the components that you have installed, if there's no proof lawyers can't make it up. But in this case there is the chance that the components caused the damages and if so you're stuck. That's why it might not be a good idea to take them to court. A cat isn't very expensive so it's probably not worth it, but if they blamed your CAI for blowing up your engine that would be worth it, because it is very likely that the CAI wasn't the thing that blew the engine. The Moss Warranty Act is very clear on what dealers can deny coverage for and the courts are very uniform in their rulings, so it's very hard for even a good lawyer to convince the courts to go against precident.