Looking at '88, '89 Vanagon electrical diagrams in Bentley, the O2
heater element grounds at engine bay.

O2 body is the ground for the sensing element. It grounds through
exhaust. The shielding wires (aka "reference ground" ?) around the O2
centre "signal" wire connect to ECU then split off to a ground point
at engine block near distributor or at oil breather tower base.

If it were me, I'd look at those points first and inspect the shielded
O2 wire. Sometimes the casing cracks on the inner wire and shorts to
the shielding wires. See some images I posted of my '88 green O2 wires
here:

https://picasaweb.google.com/musomuso/New1988Westy#5748856721901671282

At one point I added a new wire via stainless steel clamp on new O2,
to vehicle frame. I doubt it made any difference in my case (new cat,
O2 etc) but maybe would on a really old exhaust?

On Sat, Oct 5, 2013 at 11:50 AM, Karl Wolz <wolzphoto@q.com> wrote:

> ..... indicating a poor O2 sensor ground.  Does the sensor ground through its mount into the exhaust, or along with the heating element ground wire?  If through the exhaust, how can I improve the connection?

--
Neil n

Blog: tubaneil.blogspot.ca

'88 Westy http://tinyurl.com/c8rlw6p

'81 VanaJetta 2.0 "Jaco"  http://tubaneil.googlepages.com/

Vanagon VAG Gas inline-VR Engine Swap Group:

http://tinyurl.com/d7gd5ej