Having read your post you might be able to help me, I am putting back the original headunit as selling the car.
I went to connect the plugs back in and power is present as the cd player is making a noise but no displays comes back on and no sound other than bleeting when i press buttons, I know I have to put my code in but cant do this until i can see the display. I have plugged in the black, blue and white plugs and the yellow hole is empty on the headunit, could this be the reason its not displaying. I have looked for a yellow plug but pretty sure there are only 3 to go back in.