Note: i did not test this because we did not have a blow torch or were in the correct conditions at the time.
To test an O2 sensor i would of had to clamp a specific O2 sensor in a vice, on a zirconium type which has two wires which are an earth and and output wire, and attach a multimeter to it with the black lead to the black wire (earth) and the red to the red wire (output) and measure the output in DC voltage. To change the reading i would have to heat up the perferated end of the sensor with a propane torch. once heated after 20 seconds you should get a reading of atleast 0.6v but if not it is an open circuit due to fouling etc. within another 4 secs it should drop about 0.1 of a volt.
