how do you check an O2 sensor?

[S13squirrel]

Is there any way to check the functionality of an O2 sensor on my own? Can I use a voltmeter? If so, what voltage range am I looking for? Can I look at the sensor for any visible defects?

[getsideways77]

Take the o2 sensor off look for carbon deposits and then get a multi meter and hook it up and put it on dc volts and get a propane torch heat it up till its red hot focusing the flame on one side which ever has more carbon built up on it heat it up then take the flame off and when hot the o2 should put out a volt reading of .94 to 1 volt and then immediatly drop voltage when the heat is taking off. if its getting a good reading you could try cleaning it up by putting the propane torch as hot as it can go and hold it like a half of an inch away from the tip and youll see the flame change colors and you will actually be burning off the carbon making it alot more responsive then go and check it again and see if you get a better voltage drop when heat is taken off it

[BLT123]

Shake it - if you hear something loose inside it's busted. Easiest way to tell.