O2 sensor

[cwagner at info2000.net]

I have a question about how to tell when the computer is in closed 
loop mode when a person doesn't have a scan tool.
I built one of the O2 sensor gauges using the LM3914 chip.  What 
should I be looking for to tell when closed loop is on?  From what I 
have read, I should see the gauge fluctuating several times a 
second (or as close as the eye can tell).  Also, with the O2 sensor 
disconnected from the computer, the O2 sensor does not send a 
voltage during idle even though it is a heated sensor.  I find this 
interesting.