Hi Brett et al involved.

Thanks for posting what you're finding. At best I know little about
all this but know enough to appreciate some of whats involved. I find
this an interesting thread.

An image from my Digifant pro training manual showing labelled pin
outs of ISV control unit:

https://lh5.googleusercontent.com/-QxW65MiNQlI/UoUHgd3ioUI/AAAAAAAAIp0/rfGr1KsYiho/s512/ISV%2520diagram%25201.jpg

Hope that link works and diagram is legible. I can p-mail a higher
quality image if you want.

Neil.

On 11/14/13, Brett Ne <brettn777@gmail.com> wrote:

> David Beierl sent me a picture of an oscilloscope tracing from the coil
> primary circuit during firing and boy, is it ever anti-friendly to
> microcontrollers!  There's a decent spike up around 30 volts and a very
> brief spike of over 200 volts!  Fortunately, we don't have to worry about
> that.  Initially I assumed that since the tachometer in the instrument
> cluster is driven by the coil primary signal, that the tach info to the ICU
> would have the same source, but it turns out that it gets tach info from a
> common connection (with the ECU) to the output of the Hall sensor.  The
> Hall sensor won't be above 12 volts(keep in mind that in a car, 12V could
> really be anywhere between 9-16V).
>
> So, I've spent some time looking through Bentley and looking at some other
> sources online to sort through the various connections to the ICU.  Below
> is a listing of what I've found.  Please look through for any mistakes or
> misunderstandings.  The terminal numberings are those used in the Bentley
> wiring diagram for the Digifant 1986 system.
>
> ICU(Idle Control Unit) connections:
> 6/50  Digital input from the starter switch
>         high when starter is engaged
>         low when the starter is not engaged
>
> 14/15  12V power supply to the ICU whenever the ECU has power
>            Also supplies power to the power steering pressure switch
>
> 15/LH  Digital input from the power steering pressure switch
>            high when power steering is engaged
>            low when power steering is not engaged
>
> 5/31  Ground connection to the ICU
>
> 13/T  Analog input from the coolant temperature sensor
>
> 8/LS  Digital input from the throttle valve switch
>          high when throttle valve closed or wide open (I'm guessing here)
>          low when thtrottle valve partially open (I'm guessing here)
>
> 4/ST2  PWM output to the idle speed stabilizer valve    Note: One of ST1
> and ST2 is an ground connection and the other will be a
>
> PWM power source. Must be tested to see which is ground.
> 11/ST1  PWM output to the idle speed stabilizer valve
>
> 2/K  Digital input from AC compressor
>        high when AC compressor is on
>        low when AC compressor is off
>
> 17/1  Analog input from the Hall sensor   What is the typical for the
> baseline voltage and the peak voltage?

--
Neil n

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