Success...
Set switch on XDV-P90 from IPBus back to Stand Alone, back to IPBus, press reset button each time.
Start with XDV-P90 power off via it's own remote.
Allow Avic D1 to power up XDV-P90 via IPBus. Should get audio using S-DVD input which should now be an INPUT option.
Set Video input on Avic D1 to M-DVD to get video.
Exactly per the manual, just remember to reset the P90 DVD player as well everytime you move the rear switch from Standalone to IPBus.
BTW, there is no AV Bus cable on the XDV-P90...