yes there is a possibility of damage to the ecu,  also you will disrupt
the ecu in its attempting to balance the engine causing swings  rich or
lean as it tries to adjust to the new signal levels received.  this
means that when you take it out of the circuit the ecu will go rich or
lean and the meter for the sensor will read the new condition and not
what it is when the sensor is in the circuit.. suggest finding a way to
put a second one in or use some sort of high impedance bridging.
jimt
On Tuesday, Nov 12, 2002, at 08:33 America/Denver, Jay L Snyder wrote:

> I am thinking about running two wires to the front to a digital
> voltmeter
> from the O2 sensor.  If I looped the signal from the sensor to the
> front
> and then back to the ECU, I could interupt the signal to the ECU from
> the
> front with a switch.  This way I could monitor the mixture with and
> without
> the O2 sensor on-line (closed and open-loop).  Am I looking at any
> potential damage to the ECU by shutting the sensor's input on and off?
> This would be no different than an O2 sensor heating up or failing in a
> normal wiring scheme.  I plan to run wire from sensor (I have an '85
> w/single wire) to the voltmeter and also to a switch.  From the
> switch, run
> a wire back to the ECU spade connector.  Any problems? Probably only
> need
> small gauge wire, maybe 20 AWG?  This would allow me to tune the AFM at
> real driving conditions.
>