Hu you should be seeing 12v from pin 17 when in d and no volts from pin 18(pin 18 is used with the accord tcm but not the lude tcm).

Do this cut the yellow wire pin 18 but leave enough wire from the connector so if we have to but connect the wires back together.If any problems appear re connect them.
Let me know if that works im only going to say 30% on this one it is not going as easy as i hoped.If not do you know how to do a continuity test the next step would be to check the input to the computer d4 indicator.

Now you did say the d4 light worked with the swap but with the accord tcm but not the lude tcm correct.