I don't know if it was at the steering column harness or not. It was the bundle of wires that matched your list and colors the closest. It was the bundle in the 2nd photo - which is located at the TOP of the steering column.
I did not test any of the wires in the flat ribbon wire (which did NOT have any yellow wires -1st photo) - this one is running inside a vinyl-tape-like cover at the bottom of the steering column.
Forgive me if I misspoke - just to clarify - I have not personally jumped anything. The so called mechanic "jumped the starter" - HIS words.
All I have done is plug in wires after the steering column was installed by the mechanic who left me with this.
I have not yet laid eyes on the starter, but I am about to go crawl under and see what I can find.
Once I find the starter, I'm hoping I can successfully find and test the yellow wire there.
And again, forgive the stupidity - can u tell me what and where the " Firewall Plug PIN 31" that you mention is?
Found the starter, I think. The solenoid seems to be attached - there are 2 posts - one fatter squarish feeling one (cannot see, only touch) with a large red wire attached to it, one skinny pointy post with a skinny black wire attached to it.
Big square post = 13.+ at rest, 12.9 at crank position
Skinny, pointy post - 0.0 at rest and at crank
I also located the starter relay on the fender - tried to test the skinny yellow wire coming out of it - 0.0 at rest and at crank - but I'm not sure I got a good connection.