Which sensor is bank 2 sensor 2 - 612

Bank 2 is the left bank (cylinders 7-12). Sensor 2 is the sensor on the left rear exhaust manifold (cylinders 10/11/12). You did not specify if if is a front sensor (in front of the catalytic converter or a rear sensor (after the catalytic converter). You need to know which one it is, as there are two oxygen sensors on each exhaust manifold (eight total on the car). On a 612, the rear sensors are very difficult to access.