You want to verify AIR system is coming on before doing a 02 changeout..the 02 is just the feedback testing device that monitors the AIR system.. if the pump is not running when it should, the 02 sensors has nothing to report.................the first question to look at would be is the pump even coming ON ???
Your problem could be as simple as a bad fuse or broken vac line.
As Carl stated , the 02 sesnor will fool the guy doing the diagnostics when ALL ELSE in the AIR system seems to be funtioning properly, BUT you still get a code ..so, you have to verify the system first before going right to the 02 sensor...if the system/pump is not even coming On , the 02 sensor is the last place to look.