I was having problems with mine and found a test on Google.
"All you need to test an oxygen sensor is a propane torch, vice grips, and a 10 meg ohm input impedance meter capable of measuring low voltage (1 volt and less). If you are going to buy one, ask for a high impedance (10,000 ohms) digital type.
Connect the voltmeter. Then heat the tip of the sensor, holding the tip completely in the flame. Move the torch flame over the sensor tip. The tip should be hot enough to turn cherry red, and the flame must enter the opening into the sensor tip.
Meanwhile, keep an eye on your meter. If you get a reading above 600 millivolts, and the reading quickly changes with the movement of the flame over the tip, the sensor is OK. Otherwise, replace the sensor."
After doing the test my O2 sensor worked great. Probably because it burnt all the crap off of it. Then it died a week later and failed the test.
It will give you some thing to do until you save for a new one.