DMM and O2 sensor

[Tom Cloud]

I've never heard of this .... is this true for all controllers,
or for certain ones?  The concept is reasonable to me, but certainly
not necessary that it always be done that way (i.e. sense for an
open EGO).  I would think a constant current could also be used.
In fact, it is my understanding that a constant current fed through
the EGO can help derive data that allows compensating the EGO
output for differences in temperature so that A:F readings can
be more accurately made off-stoich.

>Hi Guys
>
>An O2 sensor is usually fed with a very hi impedance DC voltage
>of about 0.45 volts from the ECM. In a fault condition if would remain
>at 0.45 volts indicating a inactive o2 sensor. The impedance of the
>voltage divider network is about 10 megs. Thus a 10 meg meter
>would read about 0.35 volts. This has actually nothing to do with
>the O2 sensor itself.

Tom Cloud <cloud at peaches.ph.utexas.edu>