The PCM completes the circuit to ground through the terminal C6 identified as reverse inhibit solenoid. I would do a test to make sure that it works as advertised as the car was an auto trans. Someone on the board may have more knowledge about the various programming details of the PCM. The PCM may need to reflashed or something for a man. trans. feature to work.
To test you can probe the C6 (lt. green wire) terminal with a test light to make sure it go to ground above 3 mph.