4ks OXS-system connector problem?

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <00BF1F2FEDFED011A27D00805F91E3C20D7741@ABK-NT01> "Hare,Stott (X)" writes:

> If I understand what you're describing correctly, you'll find no
> matching connector.
> That is a test tap, used to read the duty cycle (dwell?) of the OXS
> sensor.  This
> connector provides a means to set fuel mixture, usually set in
> conjunction with
> ignition timing...

Scott Mockry (whose silence is impressive) has recently deduced and 
demonstrated the reason for this.  The (fuel) frequency valve (Taktventil) is 
driven by the ECU via a resistive lead.  Because the valve is an inductive 
load, the waveform that results at the valve's connector - while the traces 
make perfect sense to the human eye - simply fools all extant duty cycle and 
dwell meters.  You can't make reasonable measurements at that point using the 
sort of meter that you and I might buy.  The sort of stuff that Scott has 
access to ...
 
For those vehicles in which the duty cycle measurement is important (in 
principle, the North American variants) Audi has provided a test point by 
taking a non-resistive (don't pick nits - all wire has resistance) lead from 
pin 8 of the ECU into the engine bay.
 
At least two UK vehicles now have this test point.  Experiments continue.

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club