2003 Toyota Avalon Check engine light code P0155

Check engine light on for last few months. Needed inspection done, so I took to o'reilly and they said, Code P0155 is Bank 2 Sensor 1 Oxygen Sensor according to o'reilly auto parts.
So, I replaced myself, with Bosch 13540 bought at o'reilly for $169.99 (way overpaid now that I check online prices). Check engine light still on. So I stopped in an inspection place, they reset the code, and it immediately popped up again. Looked online, someone suggested to check the fuses (somewhere I read that).
So I pulled and inspected all the simple fuses that seemed to be connected to emmissions.
Then, when I started the car, the check engine light was off (1st time it came off in 4 months).
But, went back on after 30 seconds. So, I figure I cleared the code by removing power (by pulling the fuses), but cause is not fixed, so code came back on. Need some advice on how to proceed.
I also found it outrageous that Midas quoted me $300 to fix when it took me 20 minutes to replace the oxygen sensor. Of course, now I have spent $170 and still do not have it fixed. Any suggestions GREATLY appreciated!