small black wire near distributor w/ rt-angle fitting attaches where?

[chembrad]

1994 4.3L V6 vortec, auto everything.

Right behind the distributor there is a wire cluster that comes through the firewall from the cab into the engine compartment.

There is a small short black wire with a right angle fitting that comes off of the wire cluster.

I cannot figure out where it attaches.

Anyone know the answer to this?