P0420

[@camaro_szn]

So a few weeks ago my check Engine light came on with a PO420 code. I let it sit for a few days just to see if it’ll go away and when it didn’t I went ahead and replaced the O2 sensor which had no effect on it. 2 days ago I put cataclean in the tank and the light went off for 48 hours but now it’s back on.
Any suggestions besides replacing the Cat with a stock one? I don’t want to spend the money on replacing it with a stock one when I have plans for BBK headers that come with 2 high flow cats I just want a temporary solution for the time being.

[LETZRIDE]

What cat is on there right now? And which O2 sensor specifically did you replace?

Are you out of warranty from GM to have the cat replaced? I believe it is 8 years and 80k I believe.

Have you tried cleaning the MAF at all?

Lastly, as a bandaid fix you could go and buy spark plug non foulers from the parts store. I believe the 18mm tapered version will fit the downstream O2 sensor. Install it and it will push the O2 sensor at the rear back more and generally cause the code to go away. That being said, I am not sure how they will fair in a visual inspection...