Now there's definitely some short in the wiring.

If I'm measuring voltage on the white (right) terminal I have 12 volts on pins 4, 5, 6 and 12.
Now if I plug in the blue connector ( X18362 ) into the PDC, I lose voltage on the white connector terminal right away.

So basically the PDC stops outputting voltage to the rear sensors as soon as I connect the connector for front sensors (X18362).

This tells me where's some kind of short it the wiring that goes to the blue connector.