Do You know how to check Heated O2 sensor

Is there a way to check if my Heated O2 sensor is good or bad? I reset the codes with my OBD II tester. Not sure if Service Engine Light will come back cause I haven't driven the van a couple of days. I read someone elses post about him changing that sensor because of the code he got and the SES light came back. I dont' want to change it unnecessarily. What would cause this sensor to go off? Any clues where to start? Also if I erase the code do you think the computer will be able to read in DMV before the light comes back? Will the code show again?

Thanks for any help guys.