I found this good tutorial on old Chrysler ICM's this morning.
Chrysler Electronic Ignition 101 Note that someone said that the 5th pin on newer units are dummies.
That extra pin is no mystery.
One is powered in start position and the other runs through a ballast in the run position.
The old 5 pin modules were poor in fact they couldn't limit current on their own. The 4 pin can somewhat, so only needs 2 pin ballast. The replacement modules are 4 pin type and don't need the 4pin ballast. May have a 5th pin, but it's just a dummy pin that leads to no where.
That seems risky since most people would just think it was a direct replacement, however you need to rewire your system and switch to a two pin ballast resister. Or, maybe you don't NEED a two pin ballast, you just can use one? Perhaps it is in the instructions for the ICM.
