Hi all. I recently bought a 2002 Camry with the 6 cylinder 1MZ engine and it drove great no issues for the first week. The thermostat was stuck open so I replaced it and in the process unplugged lots of hoses and harnesses to get to it. A couple days later when accelerating onto the highway it threw a PO171 and PO174 code, mixture too lean on both banks. I also noticed that the long fuel trim was getting up to over 40% when accelerating. I double checked that everything I took apart was put back together exactly as it came off. I can not seem to get rid of the codes.



O2 sensors are reading proper voltages, except when coasting they read 0. MAF was cleaned and reads about 4 g/s at idle and gets up to about 35 when accelerating. Short fuel trim values are staying within +/-10%. I visually checked all hoses and didn’t see any visible defects, though may buy a smoke machine to test if codes persist. Is the 40% long fuel trim a result or a cause of my lean codes? What should my next step be? Any help is much appreciated.

 

Since both codes check for common issues between cylinder banks that could cause a lean mixture.

You stated you checked but given the codes started after the repair would make double check for issues. Cracked vacuum hose, damaged engine air intake pipe, reversed hose connection on a VSV, misaligned air intake boxes, etc.