CN2 looks like it's got frequency step input controls. 5 or 10 Hz up or down. And a common / ground?
Still not seeing the comm line to the IDU.
So maybe those Up & down lines get bumped by a controller that runs the IDU? fed by IR remote..
Or maybe the IDU runs as a Stand-alone, using Fan-mode? (Sanyo IDU works in Fan, without anything but 230vac)..
Is CN3 the 4way-valve control line??
Maybe I can get someone to translate some of this for us. I'll post if I get any info.