CIS experts-click here

Alexander van Gerbig Audi_80 at
Sat May 5 14:21:12 EDT 2001

    If I'm not mistaken the ISV needs a signal from the airflow
potentiometer to work, but that is just something I think I might have read
somewhere.  The ECU needs to know where the airflow plate is at all times to
control other functions like the CSV and ISV.

    I just checked the Bentley and it does say to check the potentiometer if
you have erratic idle.  This obviously means to me that the potentiometer
plays a role in ISV controls.  If you look in the pin out test for the
wiring it does show a test for airflow rest position on the potentiometer.
It says something like 6k ohms at rest, so I bet you need voltage running to
the potentiometer and you need it have an resistance reading coming back to
the ECU for ISV and CSV function, CSV functions when the car starts, 12v
charge for 8 seconds or less and the ECU tells the ISV to let more air in
and in turn the airflow plate rises up more causing a change in the
potentiometer resistance, right?

    I would say that the CIS-E III system is not going to be happy with
things just unplugged.  To control idle and other ignition functions I think
it likes to have input from all it's little components.  Have you tried
output test and code dumping yet?  I guarantee you get the potentiometer
code and it states in the Bentley that will cause high idle(usually a sign
of a non powered or disconnected ISV) and erratic idle speeds.

    Try plugging in the potentiometer with the airflow plate at rest, then
look for 12v at the ISV.  If that doesn't work then plug in each component
one by one and find out which one the ECU may want to hear a signal from.
If that doesn't work try another ECU if possible.

Good Luck!

Alexander van Gerbig -- '88 80

The Audi  80 Pages-----------------

North Ferrisburg, VT 05473

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