No you shouldn't have to; I only have the TCM "1" and "N" pins wired as on my circuit diagram:Do I still need to wire the shifter connector pins together to mimic neutral ?? because I left them alone... won't this cause a CEL ??
I just left the remainder of the shifter connector pins unconnected and I don't have any problem.
Recheck your wiring for the above circuit. You wouldn't be getting that P1590 or P1591 code if it's working properly