wishful1

I have a 96 LS400 and I'm getting code PO420 Bank1 and PO430 Bank2 Catalyst Efficiently below threshold. Can anyone tell me which 02 sensor these are. I know there are 2 in the front and 2 in the back, but I need to know what Bank1 and Bank2 means. Thanks for any help.

Thanks SK....what is a motorvac?

Thanks for your sugggestions. I will check the O2s.

The code for my converters are PO420 and PO430. I need to replace both of them.........does anyone have any suggestions where I can purchase used or new ones besides the dealer. Any suggestions are appreciated.