I have an 06 Aveo. It's not a hatchback.

I recently replaced the coil pack and before I could manage to do that, I drove it on misfires (one cylinder maybe) for several weeks. I know, I know... but I didn't have a choice. It was either go to work or don't. I'm sure you know what I mean.

So now that I've replaced that coil pack and I have all my cylinders back, I get a sketchy P0420 code. Sometimes it is active sometimes it isn't.

So I got obdwiz and the scanner and ran a diagnostic today.

The upstream o2 sensor looks great... it's a pretty solid waveform from .1 to .9 v. Seriously looks pretty much like this:

^ ^ ^ ^ ^

The downstream o2 sensor looks roughly the same. More like ^-^_^-^^-... something to that effect.

Essentially, they kind of mirror each other. BUT my P0420 code has disappeared this morning. I'm sure it will be back though. It has done this before.

The temp on the cat is between 1200 and 1400 degrees while scanning. The mean voltage on both my o2 sensors is at .05 volts.

Everything I'm reading in this data tells me I burnt my cat out while I was running on misfires. I've read several places that that excess unburnt fuel will kill a cat, especially in these models... something to do with terrible substances in the cat, whatever.

Do you guys concur or should I look at something else first? Bad cat, right?

Also, if you guys do think it's a bad cat, what's the cheapest new cat you'd trust here:

Chevy Aveo Catalytic Converter | eBay

 

you most likely need a cat. one thing you could do is measure the cats inlet and outlet temp with a temp gun. take your measurements with the engine at operating temp and the engine running at 2000rpm. the rear of the cat should be 10%hotter than the front. if they are the same replace the cat.


cheap cats have low oxygen storing capacity...which will result in a reset p0420...so don't buy a cheap weld in convertor.

 

Thanks for the help. I'm going to order a new cat.

I shouldn't worry about the pipe itself, right? Just the bolt in cat?

So I only need this:
Chevrolet Aveo AVEO5 1 6L 2004 2005 2006 2007 2008 Manifold Catalytic Converter | eBay
Or:
2004 2005 2006 2007 2008 Chevrolet Aveo Catalytic Converter 1 6 Front Direct Fit | eBay

Not this:
2004 2008 Chevrolet Aveo 1 6L Direct Fit Front Flex Pipe A T Made in Canada | eBay

Or does that depend on if the stock cat is welded to the pipe or bolted in? I haven't even had a chance to look at it yet, but I plan to tomorrow. Or are those specifically the cats you wouldn't recommend?

And I won't buy from ebay, more than likely, but those are the best examples I can find... and I don't want to walk in to a parts store and walk out with a might as well be ebay item...