I have a 92 dodge dakota with the symptom that when the engine gets warm
it loses spark. I have the manual and have followed the diagnostic
procedure to the point where I need to test the output from the ECM. On
this model, pin 19 of the ECM controls the ground to the ignition coil
to fire the plugs at the proper time. The manual says something to
diagnose this that I can't understand. They say to make a little jumper
with a 33uf capacitor that is used to ground pin 19 and ground the coil.
When the ground is removed, if a spark is seen at the coil cable (I
assume they mean secondary), they say the ECM is bad.

Can someone explain the logic of what I'm trying to do. I understand
what the ECM is supposed to do, but I don't understand how to know if
it's doing it, even with this little jumper gizmo they describe. I'm
fairly electronics literate, but not a wiz.

There are no stored error codes at any point in the failure that I have
been able to observe. All help appreciated
thanks