Disco240

Okay so I have a strange scenario here. I offered to help a friend install his
S14 SR in his S14. He bought a harness somewhere online and I think that it may be wrong. I have never done a 14/14 swap before but here is what I have. I know that you have to extend the O2 and MAF, you also have to rewire the wipers and repin the SR dash plug to match up with the KA dash plug. No big deal on any of that I have that figured out. But I have a mystery plug hanging out on the harness and cant find anything on it. If you have any idea what this is please let me know ASAP. I have been told that it may be for something related to an auto trans controller. In the picture you can see the ECU plug (blue), the dash plug (large white plug), the relays, and then the mystery white plug. The mystery plug looks exactly like the dash plug on a S13. Does anyone know what this is and have a pinout for it. As long as I know what I am looking at I can wire it however it needs to be wired. Also the part number on the harness looks to be 2401166F04. Does anyone know if this is a true S14 SR20DET harness or something off of another SR vehicle.