Wiring help for Engine Coolant temp

[tinsoldier]

So I bought a used harness from a guy. I am trying to sort out the wirings. Well for some reason the ECT (engine coolant temp) was missing. I went to a junk yard and found a plug. My question is. I have identified the pin 74 from the blue connector c1 as the yellow wire (that is the ECT sensor signal). Where does the black wire goes?

Does the black wire go to ground? I can't find any pin on both the blue and red connector for the black wire of the ECT.

This is a 2001 truck harness.