Well this is a real head-scratcher. I left the engine running and used spray-bubble soap on all the lines to check for any leaks. None. Then opened up the top of the Pro-Vent and clearly there was tons of fumes/exhaust coming from the PCV system. Put the top back on, disconnected the hose that leads into the intake with associated sensor. Visible exhaust coming out of that (less white as obviously going through filter. So mechanically, everything is working as advertised.
Not sure why I constantly get this PCV disconnected CEL. Does anyone know what exactly that sensor is measuring on the intake tube that the PCV exhaust goes through? You guys in Australia that have the Pro-Vent with his diesel and doesn't get a CEL. Then again, you have different emissions systems on their diesels. So strange this issue...
EDIT: Looking at the Aussie pics above, looks like US Diesels have another sensor that they don't:
The sensor in question is just to the left of the intercooler hose and has a label on it. There is another output on the air/pump or crankcase ventilator system that isn't on the Aussie pics. Wonder if that is what is causing my problem, and how does it know I have a catch can installed?