Originally Posted by macgy

Guys,
I hv the same P0420 code about 2 years ago, I just changed the PCV, the engine light didn't come back until today.. I m going to change another PCV next week, I will update again after 1 month or 2 if the issue is resolved.

Originally Posted by infamous107

Well after months of battling this “p0420” code I FINALLY found a solution to get rid of the check engine light after replacing part after part associated with this code. I was about to give up and hand over 1400.00+ to the Audi dealership until I ran across one more solution. I started reading on information concerning an O2 spacer for the second bank. This spacer I guess, gives the O2 sensor a gap so that the temperature coming out of the aftermarket catalytic converter reads within limits and “poof” engine light be gone!!! So once again I have to thank this site on saving me about $700.00 and some change. Took me a little to figure this one out, but the cat was initially on the quits. So if you guys are on the same troubleshooting boat with this code and you have done EVERYTHING in its power, give the O2 spacer a try. I bought it for 23 bucks off a german parts website. Now awaiting my next check engine light troubleshooting issue…lol.