Autozone test I needed my OS2 sensor replaced, however, I find that there are 4 OS2 sensors. How do I find out which need to be replaced? 96 Ford Taurus Wagon 6 cyl

Autozone said it was OS2 sensor but there are 4 of them. How do I find out which one is bad?

First understand that these test are in lack of better terms misleading as the issue sets off the code for O2 while the issue is likely a vacuum leak or dirty fuel injector or bad spark plug or dirty air filter ect, so while your know O2 is suggested review all possible causes for O2 code to be set before replacing the sensor or sensors.

While the test will show which O2 is suggested this is read out as Upstream/Downstream & Bank 1 or 2. Locat what the test result is to better understand the symptoms and therefore the causes and where to look for your issue which likely is not the O2 and a waste of money to replace without knowing there is not a reason other than the sensor is at fault. While saying this understand that it is wise to also check the O2 wire harness and connection points as part of your diagnosing. No reason to pull it out and try to clean it or inspect it. Tell me the result of the test as best you can as it was tested so I can know the common issues to give as possible causes to set the code giving.

BTW is the check engine light just on while engine runs fine otherwise or is there also a poor running engine?