I have done some research and I can not find a clear anwser.
I am swapping to a manual from an AOD in my 1989. The T5 has a back up light wire and another plug... what does this plug do? There is only one plug under the car which is the backup.
The other plug is going to be your neutral start switch. This tells the computer that the car is in neutral. Main reason is for pulling codes. In order to have this function, you need the 5sp harness that connects in the driver kicks panel and runs to underneath the car. It will include plugs for your VSS, back-up lights, and neutral start switch.
thats correct,just did the swap on my car but didnt have the harness.so what i did was take the old back up light plug and made myself a new harness for that and the other 2 wires i just connected together so the car would start without pushing the clutch in.i dont remember exactly which wires are which,there are 4 but the black and 1 other are reverse and the other 2 to start.put the car in reverse,key on and have a buddy at the back of the car.touch the black wire to each of the remaining 3 till you get lights on back there.then connect those 2 and the other 2 are ignition.