The third connector is the seat belt sensor. Taking the seat apart now to get the weight sensor out.
There are Three plugs on the passenger side seat in a 2012 Nismo.
Yellow Plug = Airbag (use the resistor)
Skinny White Plug = Seat Belt (runs to the seat belt, pretty simple to find and replace)
Medium White Plug = Weight Sensor (remove and replace in the new seat and plug in)
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