Have a problem with po174 and p0154 check engine light codes. I have already changed 2 post cat 02 sensors and problem is still there.??????

 

P0174 - Bank 2 Lean

Check for a clogged, dirty, or oily air filter
Check/Clean/Replace your MAF

P0154 - o2 Circuit No Activity

Check the wiring for the o2 sensors
Could be as a result of P0174 (fix that first)
Check for shorts and proper grounding of the sensors.