Zirconia O2 sensor alternate modes of operation

Orin Eman orin at wolfenet.com
Sun Feb 22 08:26:10 GMT 1998


> I think it is .456V supplied through 1Mohm. When the sensor heats, it's
> resistance drops and can now overcome the bias voltage. The .456V is just
> there to fool the ECM until the sensor is warm.

And to help detect a dead/open circuit sensor.  If the O2 sensor
voltage stays around .45V and the engine is warm, it's a pretty
good indication the sensor isn't working.  (Using a high or
low bias wouldn't work since you wouldn't be able to tell the
difference between a permanently rich/lean mixture and the
bias voltage.)

My car seems to bias the sensor to .4V thru a 684k resistor,
at least I seem to remember seeing .4V when I put a DMM on
the terminal with the sensor disconnected... and it's what
I figured it to do too.

Orin.



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