One thing I should have mentioned is that it does take a couple of minutes for the 02 sensor to heat up before you get a proper voltage from your voltmeter, so you will have to let the engine warm up a couple of minutes.
You can experiment with the 02 sensor if you clamp the sensor in a vise and hook up the voltmeter to the signal wire and ground on the vise. You can then use a Propane torch and heat the part of the 02 sensor that sticks inside the exhaust until it is bright red. Once it is bright red then wave the torch over the 02 sensor and see what the voltmeter is reading to get a visual idea of what is going on. You can then relate what you see to what is going on inside an engine and maybe get a better picture of what is going on.
Just don't burn any wires or hands.
Adam
