Well, now that the Mustang is done, I did a little more wire tracing last night.
Highlighted orange is the yel/blk wires I am trying to follow, highlighted green is the wire I want to interrupt.
In my hand are three relays. The brown one is PGM-FI Main Relay 1, the blue one is PGM-FI Main Relay 2, not sure what the other one is. One yel/blk from each relay goes up and connects with two more yel/blk (this junction is just to the left of the PCM and is wrapped in blue shrink tube). One of those yel/blk goes to the immobilizer (left of the picture) the other is supposed to go to C102. The wire that is supposed to go to C102 is flagged with some electrical tape.
Which brings me to where I am stuck at. The gray, 20-pin connector (looks white in the pic) just right of my wire marked with tape... is this C102? I can only find two yel/blk wires, my marked wire and one that appears to go under the hood (but this one is far more difficult to follow). According to the diagram, there should be two more going to IGP1 and IGP2 on the PCM. I can't find these. The wiring diagram has the caveat of "except GX & HX" and it's possible my HX doesn't have these wires. I'm concerned that if I interrupt my flagged wire, I may also interrupt the IGP1 and IGP2 to the PCM which may trigger a trouble code or something.
Any thoughts?