In a full-function (closed loop) fuel system that uses either an electronic controlled carburetor or fuel injection, the O2 sensor acts as a final check on the other fuel metering devices like throttle position, absolute pressure, coolant temp, fuel pressure, and bunch of other computer inputs that change constantly. The O2 sensor is constantly hunting for that elusive perfect .5 volts, and it's yelling at the computer- - - - -"RICH- - -LEAN- - - -LEAN- - - -RICH- - - -LEAN- - - -ETC." and it's doing it 10 times a second or more. No matter what the computer does to adjust the mixture or ignition timing, the O2 sensor yells "You're doing it wrong, DUMMY!"

O2 sensors are female!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!