help please

[BamaRanger93]

So i just got finished swapping a fresh 4.0 into my 93 ranger.On the back of the wiring harness i have three plugs coming from under the intake.I know where the two white plugs go but there is a small round black plug that i cant remember where it plugged into.if anyone knows what im talking about any info would be appreciated

 

[94Reborn]

On my truck (94) I have the two white o2 sensor plugs, and 2 black plugs running to the rear. One is for the manual transmission sensors, and the other (which is nearer to the o2 sensor plugs) I do not have plugged in, my guess is its for the auto trans and the harness is universal between the two. Hope that helps.