I have an 04 ssr with 136000 miles. The check engine light comes on about 2 days after I clear it. I replaced the bank 1 sensor 1 with a demos O2 sensor. Because my diagnostic tool said it was the problem. Now I get 2 P0420 codes. Both saying bank 1 and no sensor number. I ran car clean through it and put seafoam in the tank when I filled up after running the cat clean through. 3 days later the 2 P0420 codes showed up again. Haven't noticed any changes in the way she runs. Any help from here please.?