2009 Traverse. I just got it recently. It came with a bad cat and I got the P0420. Upon replacing it, it seemed to work fine for a few days. Thing is the downstream O2(which is pretty new) reads like .02 ish while the other 02 reads .45(I recall), but it ran fine for about 5 days until....

Now I get P2097 and P0420. The truck purrs like a cat and looking at the plugs, they are all fine- no carbon buildup from running rich.

The 02 upstream read the same as the second 02 upstream.

I already swapped all 4 02's with same results. fyi.

Did I just get a lemon Cat???

TIA.