Hi new here just got an 2001 f-150 4.2 gas engine and the light came on saying lean condition bank 2 I checked vac. leaks and replaced the gascap but it comes back on after resetting it next I was going to change a o2 sensor but don,t know which one to try any advice will be helpful thanks

 

Bank 2 would be the bank on the driver's side. The O2 sensor would be the one under the exhaust manifold on the driver's side.