I was checking the o2 sensor today with my fluke meter and the voltage was swinging from a mininmun of .100 volt to a max of .850 volt,the bargraph shows a sweep about every second,The amm has a pot on the houseing and you can vary the response time of the o2 sensor by going lean or rich with the adjuster screw.Now I hear there is a tool that has a led that hooks to the green/white wire on the passenger side of the car and is supposed to read mixture in an "on and off" sequence,my old Ford eec 4 tester has a led and if I held the rpms steady for 15 seconds at 2000 rpm then released the throttle the led would light then shut off,is this normal or is the mixture off even though the o2 is sweeping up and down like it should.