More precisely, a plot of the voltage output of the O2 sensor vs. richness
is roughly an "S" shaped curve with the middle section of the "S" - the
place where the fuel/air mixture is in stociometric ratio - being *very*
steep.  Accordingly, as the fuel/air mixture fluctuates slightly around
"perfect" the voltage you see fluctuates wildly.
---------------------------------------------------
Tom Young
Lafayette, CA 94549
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----- Original Message -----
From: "Dennis Haynes" <dhaynes@OPTONLINE.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, April 23, 2005 12:48 PM
Subject: Re: O2-senser voltage testing

> It means it is working and doing its job.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of Leo Lee
> Sent: Saturday, April 23, 2005 1:24 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: O2-senser voltage testing
>
> To detect the voltage deliver from the O2 senser to the ECU after engine
> warm up, I connected the positive end of a voltmeter to the green wire
> coming out of the O2 senser, and negative to the ground. After engine
> warmup, I observed the voltage. A higher voltage (0.7- 1.0) indicate a
> rich condition, low voltage (0.6 and lower) means leaner condition. I
> found that the voltage continue to fluctuate between 0.2 to 0.8. Can
> someone please tell me what is this mean?
> Leo, 1991 multivan.