l got the code for a bad O2 sensor and it listed bank 2 circuit 2. which sensor do l need to replace?

The one behind the catalytic converter.

why do not you test o2 sensor.

test it on the workbench..see:

http://mr2.com/TEXT/O2_Sensor.html

the second sensor on the left hand side (bank 2) is where cyl #2 is located red colored wire green plug it is difficult to run the wire under the throttle body and down the back of the motor allow the motor to cool off before starting the O2 exchange. Only Nissan O2 sensors have all the wire clips and exactly correct sensor and plug. Have fun approx 1.0 hour can be done with out dismantling any other parts.