If the engine is rich enough to be a noticeable problem, the O2 sensor
output should be 1 volt or more. To quickly check the wiring, disconnect
the sensor. With the ignition on, measure the voltage on the wire to the
ECU, it should be about .6 volt. This is the leakage voltage at the input
amplifier. Then, measure the voltage on the shield on the O2 sensor wire.
Should be real close to 0. Correct both as needed. Then, reconnect the
sensor. With the sensor cold, turn on the ignition; again, you should see
that leakage voltage. Start the engine and watch the voltage. During warm
up, you should see it start to rise. At some point, you should see the
voltage start to fluctuate as the ECU goes close loop and tries to adjust.
The ECU will keep richening the mixture until it sees the sensor voltage
rise. It is normal for it to vary from .2 to .8 volts.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Shawn Fowler
Sent: Tuesday, April 03, 2007 5:29 PM
To: vanagon@GERRY.VANAGON.COM
Subject: o2 sensor voltage

Howdy all,

I popped a meter on my o2 sensor at the clip 24" away from the sensor and
was getting quickly changing voltages around the .3 - .4

Does this sound about right?  I also put my meter on the ground wire where
it hits the head and had a nominal reading there, .01 or so.

The engine is still running very rich- temp II sensor is replaces as well.

Is there a way to test the signals at the ECU?

Any ideas?

Thanks

Shawn

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