I pulled the motor from a 99 lumina LTZ 34000 miles and put it in a 2003 monte carlo. Both 3.8 liter . I used the harness from the monte carlo.Everything matched up but the neutral safety switch. The lumina had the external nss and the monte had a internal one so the harness has no plugs for the nss. How do i hook up the nss? Someone please help me

 

I am only guessing here... I see possibly three options (and this is not an area I know well):
- Put the original Monte trans back in
- Change to a different wiring harness
- Find the transmission connector and see if you can break out the NSS wires and adapt them to your Lumina trans.