Engine says bank 1 burning lean

Hello, "bank 1 lean" basically means that there is either a problem with the sensor that measures exhaust gases (such as the "O2" sensor you mention), other sensors that influence air and fuel mixtures (mass air flow, manifold absolute pressure sensors) or possibly more likely you could have an air intake or vacuum leak causing the engine to dump excessive amounts of fuel into the engine in an effort to keep up with the air in the engine. Testing is required to see what the various sensors are reading and start to give a repair direction.