Engine light was on with codes P0171 and P0174 and now the light is off on 2001 Toyota Avalon

Toyota technician diagnosed with the codes p0171 and p0174 and recommended to replace bank 2 A/F sensor to begin with as the most probable cause because the voltage was not correct, and replace the PCV valve and gromet. However, the check engine light is no longer on a few days later. Any insights to this problem would be greatly appreciated.

Thanks in advance,


Asked by for the 2001 Toyota Avalon