Hi everyone ! Hopefully you can help me. Around two months ago I installed a new fuel pump as I was having problems with my old one. My fuel pressure is now good and in the specified range. About an hour or two after I installed the new pump, a check engine light came on (P0172). Eventually the check engine light went off all by itself, I assumed the sensors in the car were not used to so much fuel being dumped on them in a whilst. So they took some time to adjust before turning off the CEL. That takes me till today, the check engine light had been off for around two months. Today it came back on, I took it to a mechanic and straight away he wanted to change the O2 sensor without looking at other possibilities, any help would be greatly appreciated !