I'm happy the diagram helped, Mike

The ICU may not be bad. It could be in the connector that plugs onto it though.
If you are reading voltage there, that is a good thing.

The problem maybe with the push on terminal inside the connector is not making contact.
If someone has ever pulled that connector from the ICU it is most likely the connector or connectors have been damaged. Once they pop open they are not as tight going back on.

You may be reading the wire itself but the other side of it it not attached inside.

I had this terminal scenario happen on two cars that I know of.
The one of them was my own '86, the other was a friends '84.

I went and looked at my repair just now and it was a yellow wire in the bottom left corner.
On mine, I ended up cutting the corner of the block and pulling the one important terminal completely out of that section of connector block with its rubber.
I cut a space of two wires out of the way. It appears that there is an open space above it.

I made up the end of the yellow wire with a new push on terminal along with a heat shrink tube for insulation.

The yellow wire as I remember is an important color, in all of the this, but I do not remember from where it comes from. It could be from the distributor?

I guess, I should say that they are all important or they would not be there.
Why, in all of this Chrysler's thinking, was the purpose of designing this thing into the ICU and not have it removable?
Why invent one time, push on pin connectors into any look-a-like of a removable plug, is beyond any kind of logical thinking for me.
The head person must have fished a lot, as it sure "Baits" people, to jump on it, for an inspection!

But then again, its a history that goes way back with Chrysler. Like left hand threads on wheel nuts on the left side of the car. Probably why they have stayed number three all these years!

Anyhow, something to consider besides just getting another ICU, with hopefully an intact, unmolested, wiring harness!

It's Not too much time to lose, to redo them all correctly if the block looks butchered!

But Only! in a pinch of desperation! IMHO

Phil