Might be a bad wire but I am not sure. I suppose you should see continuity from pin 4 back through the coil to the green wire side. However backprobing wires can be iffy.

Double checking:
On the ignition module, as per the Volvo page and the 944S wiring diagram
Pin 1 - goes to the green wire on the coil. Should be +12v with the key on; gets grounded to fire the coil.
Pin 2 - Ground (Brown, typical color on a Porsche)
Pin 3 - No connection
Pin 4 - +12v, also to the coil and harness (Black, typical + on a Porsche)
Pin 5 - Triggering signal from pin 5 on the DME plug. (Green?)

The module is just a big transistor (switch) that grounds the coil based on the trigger signal.
If you pull the ICM harness you should still have +12v on that harness at Pin 4 (from the harness) and Pin 1 (from the harness and through the coil).
Pin 1 should be a lower voltage due to the resistance of the coil windings (edit: too small a difference to reliably measure).

If you ground pin 1 quickly the coil should fire even without the ICM hooked up. I think. Maybe I will check on my 928S4.

OK I was not able to see the spark when I grounded Pin 1 on the ICM harness, I had not set up a very good spark gap for the test. I did _feel_ the spark. Boy howdy. Refreshing.
I was scraping a coathanger wire to ground across the knurling on a small screwdriver poked into Pin 1 on the ICM harness. You want a very brief ground, if you decide to attempt this.

The voltages and continuity were as expected but I could not see a voltage drop across the coil. Too small I suppose.

try putting a small 12V test lamp across the two coil terminals. i think you should see the lamp flashing as it is cranked. I think if you ten move it between the battery hot and that green wire you'd see the lamp flash as it is being intermittently grounded.

that might be an easy check you can do in comparing a working car to a non working one without going too deep into the harness.

if you probe wiring with a jumper and get confused you may create a short, however if you have a lamp in that wire then it lights the bulb and no short is possible.

at home I have a " dim bulb tester" all that is is an extension cord with a light bulb in 1 wire. it's in series with the cord ends. very simple device.

if I plug in some antique radio or similar, and it is dead shorted out then I know because the light is full brightness. If the bulb is partly bright then there is voltage drop through the radio or whatever Is plugged in. that's normal... . Just a safer way than plugging in old stuff and blowing breakers.. I can also change the supplied voltage by swappping bulbs to different wattages.


same principle can be sed in checking car wiring, easy to look at, less confusing than a meter that may show erroneous voltages or things like that, numbers dancing around.

occasionally Ill fed a wire with 9 V from a battery and go looking for the ends.. nothing else will produce 9 volts so I know it's not just a mistake .. if you put a 9V battery in series with a little bulb that will do for checking continuity etc. sometimes I see the little screwdriver things wit a bulb in the handle, similar idea, they work well.

Hey guys, after doing some thinking and testing I have eliminated the speed sensor spacing and the sensor because I have had this car running with how the sensor is currently spaced and the sensor is new and is putting out good results when doing tests. About the green wire not having continuity I was being stupid and reading the diagram wrong sorry guys.

For the Ignition control module plug I have tested pin 5 which receives the signal from the dme and this is the signal I got: https://ibb.co/c1bYJNM
Here is what the signal is supposed to look like: https://ibb.co/Npxxb5d
I'd say that is pretty close to the signal the module is supposed to be getting.
Getting this signal and still not getting the green wire on the coil to ground told me the ignition control module might be the issue. I have two but one was the one already on the car and one is a used one I got so I believe they are both bad.
I also did the other tests on the ignition control pins 1-5.
1-I got continuity but no signal when cranking
2-I tested it for ground and it has ground
3-nothing as you said
4-I am getting 12 volts from the ignition switch
5- I am getting the signal from the dme

I might just try the test you performed on your s4 to see if I get the same results.

I also did test e) which is in the manual: https://ibb.co/m6d3zMy
With the jumper from terminals 1-18 I got high voltage on terminal 4 which is the plug wire for the ignition coil. This told me the ignition control module was getting power, ground, and that all the connections were good on the ICM.

I ended up ordering a new bosch control module and when I get it Ill try using the 12v test lamp like you said Monkey Wrench and see if I see it flashing.

Thanks for all the help guys hopefully the icm is the issue and the new one fixes it. Its supposed to get here Monday.

The ignition control module fixed my issue and the car starts right up. Thanks again the help guys.

Nice, thanks for reporting back!

that's great. Lots of people would be standing there with a new 500 dollar DME ( ECU) which was not the issue, but your troubleshooting skills avoided that and now its a 50 dollar part basically. I bet that difference paid for the scope because you probably can't return a opened DME.