Electrical Help identifying rogue wire

Blown88GT said:

It sorta looks like the "drain wire" shield from the TFI harness. The shield is a foil wrapping. The bare wire contacts the foil & is used to make the connection at the ends. It's a complicated harness & unless you are Mil-spec rated in harness fabrication, it will make no sense. The harness in question is double shielded. Probably only one guy in the Ford electrical design department understood it.

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Blown88GT said:

It should be inside the harness that connects to the TFI. Outside the harness will not work.
Go to page 22 (or 25 at the black bar at the bottom). See G110, just to the left of the 22k ohm resistor at the bottom of the page?
That's the drain wire. The dotted oval circle is the foil shield the surrounds the wires in the harness.
Notice that there is a connection only at one end of the harness. NOT at the TFI end but close to the EEC. The schematic is not a physical so can't tell you exactly where it belongs without diagnosing a good harness.
In your picture, I can see the wires coming from the TFI. The drain wire goes with them but it looks like the foil overwrap & the tape is gone.
You can redo it, here's how. You only wrap the 3 wires shown in the schematic, DB, Y/LG, BK/O

Tape Wrapping Wire & Cable Harnesses Guide

This tape wrapping wire and cable harnesses guide covers generic methods for applying insulating, thermal or EMI tape materials which can be helically wound around a wire or cable bundle.

www.zippertubing.com

1988 Mustang Electrical & Vacuum Troubleshooting Guide (EVTM)

File is too large to upload. Here is link to it on my Google Drive. View: https://drive.google.com/open?id=1on5czXKmpETzxUggWTGtoUuVkJT2UUxN

www.stangnet.com

The single page from the EVTM is attached.

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