david, sorry to hear of the problems, especially the harness.

im not an elect expert, and do not have a schematic to help, but...

i had the N switch die twice on a previous volvo. stop at "insert favorite place here" shift to P, turn off car. return later to find car totally inop. 1st time had no clue. indy replaced switch, all is fine. approx 2 years later, same thing again. no amount of "fiddling" with the switch or shifter would enable the circuit. replaced again and it held as long as i owned the car.

i would begin at the N switch. good luck! - benton in atlanta

PS- i would think that the N switch is on a different harness. im guessing you replaced only the MAIN engine harness.