Random plug, should it be used?

Hey I just had my engine rebuilt and put back in a few times and i was up and under doing an oil change and I noticed near the oil filter is the oil pressure switch, but a little way’s down that wiring section there’s another plug hanging out and it’s not plugged in anywhere. Does anyone know what this is for or where it should go?

A picture of the plug would get you a more accurate answer.

what year integra? could be the fan kick on switch…car should be overheating. could be oil pressure switch…oil light should be on. could be knock sensor…not that important-usually. could be alternator plugs…car wont charge and one morning battery will be dead. could be crank trigger for vtec…sends a signal the the computer…important. could be steering rack pressure switch…not important. could be iacv…controls the air at idle mode…yea. have a pic?