more like the dash plug to the ecu.
SR20DET Swap Engine Harness Wiring Diagram Guide SR SR20 it's that 1st plug it says to cut the orange wire is the one that needs the voltage going to it so the ecu knows the car is trying to start. But since u have a S14 harness in your car I'm not 100% sure which wire your going to use. The KA dash plug will still be the same orange wire tho.