William,
    First I would check the input resistance to the ECU. If it is near zero
then I would suspect the ECU. If not shorted I  would force the input of the
ECU high by using a flash light battery. Do this with the engine up to
operating temperature. With the ECU seeing 1.5 volts, the output of the O2
sensor should go low.  Conversely, grounding the input of the ECU should
make the output of the O2 sensor go high (~1volt).
Ken Lewis
86 Transporter Crew Cab
60 356 T-5 Porsche
http://neksiwel.20m.com/
Vanagon tech, pixs, O2 monitor gadget
----- Original Message -----
From: "Greenamyer, William L" <william.l.greenamyer@BOEING.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, October 26, 2004 8:45 AM
Subject: [VANAGON] Drop in gas mileage update

Well, got some news.  The O2 sensor was gone.  However that doesn't solve
the problem.

Disconnected the O2 sensor.  Get .54 volts.  When I reconnect the sensor, I
still get .54 volts.  In just measuring the O2 sensor output when
disconnected, it starts out giving voltage but when it reaches temperature,
there is nothing in the way of any voltage coming out of the sensor.  When
connected back up to the circuit, I still have .54 volts.  My guess is that
something elsewhere (controller) has gone and is blowing the O2 sensor.

Recommendations?

William