I havenot run into the problem of a shorted 02 coax myself,
but i have read about it,
and I have seen a whole new coax wire tapped into the original one near
the ecu.

re " when the coolant temp sensor told the ECU to turn the heater off on
the sensor. "

Oxygen sensor heat is full time, any time thekey is on, from the main
relay, pretty sure.

scott
turbovans

On 12/28/2012 10:39 AM, David Clarkson wrote:
> Greeting vanagonauts. I recently (approx 500 miles ago) replaced my O2
> sensor after having a problem with my 1990 Wesfalia that caused it to
> bog down and quit running after warming up. I am assuming that this
> happened when the coolant temp sensor told the ECU to turn the heater
> off on the sensor. When I unplugged the sensor the problem went away.
> Since my sensor had more than 60K on it which is the VW replacement
> interval, I replaced the sensor. After Installing the sensor
> everything seemed to be back to normal. One other bit of info that is
> worth mentioning is that I have an O2 sensor monitor that indicated
> that everything went completely rich when the problem occurred. It
> showed this type reading with the original sensor issue and the new
> sensor issue. My thoughts are that the problem might be with the small
> guage coax type cable that sends the sensor signal to the ECU
> grounding out from the inner sensor wire to the outer metal sheathing
> that I believe is grounded to the chassis. I had a similar problem
> with this cable once before and I believe that I cut a small piece off
> of the end and put the connector back on. Knowing that most types of
> coax cable will eventually fail, I am wondering if anyone has had a
> problem similar to this with this cable and if so where did you find a
> replacement. I believe  that it is wrapped with the other wires in the
> main harness section that goes to the ECU so I would probably just run
> another piece that would be wire-tied to it rather than risk
> disturbing the rest of the original harness and causing a problem with
> another wire. Maybe there is another problem. I think that if it were
> a problem with the not so old coolant temp sensor I would have some
> type of symptom with the O2 sensor unplugged. I thought that I would
> pick the collective craniums of the group since,  as is usually the
> case someone has BTDT with this issue. I'm just not the type to want
> to continue riding around with the o2 sensor unplugged with the price
> of gas and the extra emissions that I would produce that are not good
> for the environment or my catalytic converter. Thanks for any input
> that you have. I am suddenly having to drive my older van a lot due to
> a temporary employment situation and it's begging for attention.
>
> David Clarkson
> 90 Westfalia about 200 mi  short of 300K-now what will I get it or do
> for it for this milestone birthday? It has been asking for cosmetic
> surgery for some time now (rust repair and paint)!
>