bank 1 - the bank of cylinders that has cylinder #1
sensor 2 - the aft/rear sensor (though it could be the other one on that bank that is bad and the computer getting mixed up)
http://www.allpar.com/fix/codes/new-codes/oxygen-sensors.html
sensor 2 - the aft/rear sensor (though it could be the other one on that bank that is bad and the computer getting mixed up)
http://www.allpar.com/fix/codes/new-codes/oxygen-sensors.html