1988 F350 7.5L C6.

The harness goes in front of the radiator and next to the battery, there's two wires that come out and one was connected to the ground on the battery. The truck won't start or run without the one being grounded and there's only two on that connector.

It's the only connector that comes out at the passenger front above the headlight near the radiator.

Upper part is the battery, lower part is the radiator hose, left part is the main harness above the headlight and the connection in question at the center, has two wires. If not grounded, the truck will not start or run.

 

A picture is worth a thousand words…

 

Those look like pins 40 and 60 power grounds for the computer... ECM. They should both go to the battery negative terminal.

 

The wires should be black with a light green stripe.