I've got a strange problem which i can't work out whats going on. I've got a B7 Passat Alltrack and I get the long beep and the flashing button when the park assist turns on. I've got an OBDEleven and doing a scan i get a "supply voltage for park assist sensor. Voltage too low" error. The sensors dont normally work (fingernail test confirms this) but when i disconnect either the front or rear sensors from the parking module they do work (I can feel them on my fingernail). But not if both front and rear sensors are plugged into the parking module. The voltage measured by my OBDEleven is 12.3V for 'Voltage Terminal 15' and 10.3V for 'Supply Voltage for park assist sensor'.

I also just replaced my battery today as i though maybe that was the issue. But its not.

Any ideas would be appreciated.