p0420 code popped up
 

Hello I own a 02 camaro v6 3.8 and the other day my check engine light came on and I took it in and both of my knock sensors and my bank 1 o2 sensor were all bad so I replaced..so today my check engine light comes on and its p0420 which has many reasons why.. does anyone have any ideas?

P0420 is catalyst system efficiency below threshold. There are many things which can cause this as you stated. Look here and start checking before just replacing the o2 sensor.:

P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)

The PCM compares the activity of the upstream sensors to the activity of the downstream sensors. The upstream ones should be very active as they read the exhaust right out of the engine. The downstream sensors should show little activity because they read the exhaust after it has been cleaned up by the catalyst. If the activity of the downstream O2's tend to follow tha activity of the upstream O2's it indicates that the cat is no longer doing its job. Replacing O2 sensors with new ones is not going to help. If anything, replacing the good downstream sensors with fouled up ones that have become inactive or "lazy", may just be able to mask the problem. However, a failing cat will soon die, and clog up or fall apart internally.

Ok I went to a repair shop and they said it was my catalytic convertor. So I replaced so now only time will tell if what I repaired was correct

Also what does engine code p0420 pd mean?

As I said, P0420 is catalyst system efficiency below threshold.