After it being apart for a couple/several years, I am trying to complete an engine swap in my car.

There is a medium to small gauge maybe 16ga yellow wire coming out of the firewall included in the main bundle exiting on the drivers side. It is in its own sleeve. One identifying feature is a connector to a 14 inch extension. Wire is yellow before and after. I am trying to figure out where it connects to. I have a wiring diagram in a Haynes manual that suggests the only engine compartment yellows are fuel pump and coil. Well, both of those are still connected. The end is grimy suggesting maybe overdrive or reverse light. I have not connected the battery yet but did try an ohm test from the end of the lead to the fuses, with the key on. What further puzzles me is that I have continuity to ALL fuse surfaces. Do I have some sort of short? or an failure in my test logic? I am going to try to reply with a photo. I haven't used the board in a couple years and remember attaching photos to be a trick.