I have error code P0420. Toyota recommended replacing A/F ratio sensor on bank 1. Did not fix the problem. Next recommendation is to replace cat converter. The car has intermittently shown this problem for the last 150K miles, about once a year. Based on what I have seen on forums, this problem is common, and often requires replacing parts until it finally goes away. There does not seem to be any clear methodology to diagnose the problem right the first time.
TRAC, VSC and Engine lights are all on on 2005 Lexus ES330
THE CODE IS SAYING THE O2 ARE READING AN ISSUE WITH CATT BANK 1 WITH THAT MILEAGE I BELIEVE ITS A CATT ISSUE
I had the same issue. Stopped into Pep Boys and they wanted $80 to run diagnostic. I asked them to reset the codes and give it back to me. Well the tech did that but also said he thought the gas cap was loose so he tightened it. Lights has been off for 600 miles now. Check gas, cap have auto zone or some other auto parts place reset the lights then wait. If they come back on then move on with what was earlier stated or spend the money on a dealer repair. BTW I have found that the Toyota dealer will so most repairs on Lexus models and they charge less than the Lexus guys do.