Sab, forgive me because I may really frustrate you here.
If I was frustrated by people doing their best to broaden their knowledge, I wouldn't have participated in this thread. I've had some awesome mentors, starting with my father, and maintaining vehicles is a dying activity. I like doing what I can to keep that spirit alive!
I opened up the FSM and worked to track down all these connectors. I found C154 is by the transmission. I went to that one and found a broken black wire. I hoped that was the cause of all my issues. It was not. I cleaned it up and put a connector on it. Picture of broken wire below.
I can't tell from the picture, but looking at the pin out for C154, that section of the harness should have three
of or four (more on that next) wires in it - one or two Black wires, one Violet with Black Stripe wire, and one Violet with White Stripe wire. Here's that pin out from the FSM:
I'm with you - if the black wire was broken, splicing it should have fixed you issue. The black wire is in the ground path for starter relay coil.
Side note - it seems that everywhere you turn, you're finding problems with that TJ. You've got your work cut out for you!
I tested from G105 to C154 on my multimeter, and had to move the dial to the 200 ohm setting. The result was 0.4.
That's still seems like too much resistance to me.
I cannot find what is meant by the C154 Manual Transmission Jumper. It seems it goes in as a black wire and comes out brown/light blue? I can't figure out how to test #2 in your diagram.
I looked into that a bit yesterday. Go back up and look at the C154 pin out above. Notice that, for a manual transmission, both pin 1 and pin 3 are the BK wire. I believe that you'll find that one of them goes to G105, and the other goes to the other pin - like a Daisy Chain. That said, I have no way of determining why that is. I also have no way to tell what happens if that jumper (between Pin 1 and Pin 3) is broken. Test resistance from Pin 1 to G105 and then again from Pin 3 and G105. Also do it for Pin 1 to Pin 3. Report back with results.
In addition, you should pull all of the wiring from C154 to the break you repaired out of the loom and inspect it. Is there a short black jumper wire between Pin 1 and Pin 3?
For #3, I tested it from the S134 connecter at the firewall to the starter relay. The reading again was 0.3 on the 200 ohm setting. Picture below.
S134 is a splice, not a connector. Harness section #3 goes from the PDC's starter relay socket to Connector C104. Splice S134 is located here:
Keep doing the yeoman's work. First, let's make sure your meter leads aren't finky. What's the resistance when you touch the red probe to the black probe? It should be 0.1 or 0.0, depending on the meter. If it's higher than that, we have problems.
Second, my suggestion is pull everything out of the looms to inspect it. Compare wire colors to a study of the wiring schematics. The way the schematics work, it's not easy to do that because there is no actual diagram of the wiring harness. You're looking to confirm that no one has screwed with the harness and for obvious damage, like that broken wire you found. Then you can use the resistance measurements to try to pin-point the source of the high resistance. Everything should be a dead short, or 0.1 ohms. Anything higher than that means something is wrong.