My '06 SS/SC Balt is throwing a P0420 code (Catalyst System Efficiency Below Threshold (Bank 1)). I figure it's the CAT, but how can I find out for sure?

I know Chevy did an extended warranty on these CATs, so I took it to them today. Found out that whoever had the car before me put on an aftermarket CAT and screwed the warranty.

So, that's out of the question. They want $110 bucks just to tell me what's wrong.

 

Take off the dp and either get a new cat welded in or bust out the old one. The p0420 code will not cause any drivability issues. Unless the ct is actually clogged which would cause lower gas mileage and higher boost levels.

 

Thanks for the response. Yea, I'm thinking I'm going to have to get a factory CAT and replace it. What's strange is.. I do have lower gas mileage than I expected (about 15.5mpg), but my boost levels are pretty low. I'm only getting 2-5 PSI city, and when I gun it, I never get above 7-8 PSI. Before the CEL and replacing my ECU, I was getting the full 12 PSI WOT.

 

Also, keep in mind, this car sat for over a year when I bought it. I wouldn't be surprised if the cat was clogged.

 

If anyone's interested, I went ahead and changed the upstream O2. Seems to have done the trick, time will tell and ill update if anything changes.