I don't know much about the Jetta system other than what I may read in
my 93-99 Jetta Bentley. Since he has it I don't see any reason not to
use the stock HO2S relay in it's stock wiring configuration between the
ECU and sensor. If he did not have it I would try wiring the O2 heater
like later 2.1 waterboxer models, from the FP relay.

Mark

Scott Daniel - Shazam wrote:
> I have a question for you.
> On this vehicle we're talking about here, 93 or 94 Jetta with ABA 2.0
> engine...........on the HO2S  ( heated oxygen sensor )  Control Module,
> there is a wire from that module to the ECU.
> So evidently, or possibly, the ECU is involved in whether or no 02 heat is
> on or not.
>
> On a vanagon or a subaru the oxygen sensor/s get their heat circuit
> energized anytime the key is on, i.e. whenever the ecu is powered up. In
> other words 'full time' regardless.
>
> So my question is, what to do you think this connection is about ?
> My guess it that perhaps the ecu tells the H02S Module to heat the 02
> sensors for the first say 15 minutes of running, and then doesn't have it
> get heat power unless the 02 sensor cools down too much at another period in
> that drive cycle.
> Any thoughts on that ?
>
> And also..........I 'would imagine' that if I wired one so it got 'regular
> 02 heat' through a normal relay , that the ECU would set a code perhaps from
> not being able to 'see' that control module for 02 heat.
> Any thoughts on that ?
> Thanx,
> Scott
> Turbovans.
>
>
>