the oxygen sensor generates its own voltage but it is NOT 12 volts.  you
will only measure 12 volts if you are measuring a heated oxygen sensor
and measuring the heating coil power circuit.

the voltage reading on a thimble type oxygen sensor should bounce between
.1 volts and 1 volt.  the more it crosses across the .45 volt "middle" the
better it is working.

jonathan

On Wed, 12 Apr 2006, Richard A Jones wrote:

>> the oxygen sensor generates it
>> own voltage and uses the exhaust for its ground.
>
> So one-wire is 12V, and 3 wire has wire 2,3 for the
> heater.  Again, see Ken Lewis's site for great info:
> http://neksiwel.20m.com/photo5.html
>
>                        Richard A Jones
>                        Boulder, Colorado
>
>
>