Odd 02 readings

I have my driver side oxygen sensor unplugged and on freescan it is giving off a reading. one 02 is giving off somewhere around 400 and the other is around 800. shouldnt it read different if it is unlplugged (from the extension)

I have my driver side oxygen sensor unplugged and on freescan it is giving off a reading. one 02 is giving off somewhere around 400 and the other is around 800. shouldnt it read different if it is unlplugged (from the extension)

If the O2 sensor is unplugged then a scanner will show 450mV. The way you read O2 sensors if you were a PCM is 0mV means the mix is extremely lean and 999mV is extremely rich.. the median value would be 450mv and mean essentially nothing(ie. unplugged). You also get the same value of 450mV when you first start up your car because the O2 sensors are too cold to read any A/F charge.