Date:         Thu, 3 Jul 1997 14:18:25 -0400
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Craig Rogers <carogers@idt.net>
Subject:      Oxygen Sensors

I'm wondering if there is a way to check an O2 sensor to see if it is 
operating properly.  It seems as though there would be a lot of variables, 
but I think that the ECU supplies the sensor with around 500mV and the 
resistance of the sensor varies, depending on the temperature of the 
exhaust.  Since the output of the ECU is current limited(I haven't checked 
the value), the voltage at the output varies and this is what the ECU 
actually measures.  So a particular CO level should correspond to a 
particular voltage at the ECU.  If we could test the CO and check the 
voltage on a number of vehicles and make a chart, then if the numbers 
correspond, one could tell if it's the sensor or some other part of the 
system that is functioning incorrectly.  If the numbers are right, then 
it's not the O2 sensor. I know that I could have saved some money with a 
trick like this, but my problem (or perhaps my fortune) is that I have only 
one Vanagon.  Is there anyone out there with access to a good gas analyzer 
(I have one of the cheapos from JC Whitney.  Do yourselves a favor and 
don't buy one.) and several Vanagons or several people that have one 
Vanagon and access?  This could also work in reverse.  If the system is 
functioning correctly, the CO level could be checked by its corresponding 
voltage at the O2 sensor and a $20 voltmeter could be used to adjust the 
CO.  That would be a lot cheaper than other alternatives.  Has this been 
done?  Are there other ways?  Anyone?

Craig Rogers
Ineffable Audio Unity Inc.
P.O. Box 512
Riverdale, NY 10471
(914) 378-1606
mailto: carogers@idt.net