P0174 after o2 sensor change ?? Thoughts?

I recently replaced bank 1 sensor 2 and the next day I get P0174 bank 2 system too lean? I erased the code and it came back about 300 miles or so later. Any ideas?? Could replacing one sensor on the other bank caused this??



History: within the last 1500 miles I replaced the headgasket, including new intake gaskets, all new vacuum hoses and CCV hoses. Cooling system, oil filter housing gasket. Ect..ect...



Any thoughts would be greatly appreciated.