Thanks for your response.

All fuses are good - one of the first things I checked. Voltage regulator has been replaced.
My voltage checks were made with key on/engine off if that makes a difference.
And getting 12.35 at the ecu and at the control unit connector next to the 16 pin connector 9manual says 11V minimum is ok)
Not contradicting you cuz you know way more than I do, just going by what the book says.

 

Have you checked/ cleaned all the grounded wiring?

 

At this point, I have only inspected/cleaned the wiring involved in the troubleshooting procedure:
Connectors at the ECU
Shift switch connector
Shift motor connector
Gear position connector
Angle sensor connector
Shift motor connector
Shift button assembly .
Main relay and fuses
Cleaned with electronics spray and coated with dielectric grease. I haven't really looked for grounds on the frame, but will do that later today as I am reassembling everything..

Thanks for your response. Your advice is welcome.