Hey guys. So I'm getting a code. P0171 . "System Too Lean Bank One. Hoping that's tied to my engine occasionally missing. A few weeks ago I cleaned the MAF while changing the plugs. But it sounds like an o2 sensor is bad. Considering the upstream sensors aint cheap, I was hoping to figure out exactly which one is bad. I could clear the code and swap them between banks but the first time it disappeared (by itself), it didnt come back for 2 weeks. What do you think?

 

fix the misfire first

 

Do a live scan and make sure the upstream sensors on both banks are alternating between rich & lean and aren't just stuck on one side. Test it through a drive cycle to make sure the readings are consistent. If you can graph and record, then all the better; you can just go for a drive and examine the data when you get home.