How do I check if my old oxygen sensor is too worn out, not sensitive enough fo

Generally speaking, on modern computer controlled vehicles if there is no code for a sensor it is probably OK. Not always true of course and some of the older cars were not so good at flagging a bad sensor. Also lots of cars throw a code for a sensor because of underlying issues unrelated to the sensor flagged. All that being said, the best way to approach this is to know what problem you are trying to address. If it is fuel trim issues, need to check all the basics first. Then someone with the proper equipment can test responsiveness of the sensor with proper scan tools or even better with a lab scope and force rich lean and watch how quickly the sensor responds to changes. To find a properly equipped shop check Repair Pal. Good Luck Clint