This is Dave Erb of Dave's Ultimate Automotive in Austin, Texas. And we are going to talk about how to know when to change your O2 sensor. Unfortunately there's not a clear cut way of telling you how, how to know when to replace your O2 sensor. Usually when you have an O2 sensor problem you are going to get a check engine light associated with that problem. A lot of that is going to be a code for a heater circuit malfunction, that's almost always the O2 sensor itself. Sometimes it's the wiring issue or a circuit issue but most of the time it's the O2 sensor itself. O2 sensor problems can come with a host of trouble codes that may or may not mean a bad sensor. Some manufacturers recommend replacement just for efficiency sake every ninety thousand miles or so. Some cars have four or more oxygen sensors that's pretty expensive proposition. A good technician can tell you if it's a bad oxygen sensor even if the oxygen sensor is lazy or inefficient. It would be beneficial to replace it at that time. There's not really any good symptoms that would say this is O2 sensor is bad, you might notice if you over time, that it has some slight inefficiencies, didn't run quite as good when it was new. Those kinds of things but, but not a clear cut reason to replace the O2 sensor. So if you get a check engine light, and you see something associated with the O2 sensor get a good technician to check it for you properly and make sure you are replacing the right part.