What does this fault code mean?

I found this information when I did a search on Audiworld.






DTC:
01311
Data Bus Information 2)

No communication

Possible Cause:
The central unit and the navigation unit which are connected to each other via a CAN-bus are located in the navigation control module.

Internal short circuit or short circuit to Ground (GND) of a bus wire between the central unit and the navigation unit in navigation control module.

Corrective Action:
- Navigation control module does not have to be replaced if the system remains functional (the control module then switched to one-wire operation).
- The control module must be replaced if the system no longer functions.

2) This DTC indicates a databus malfunction in the internal data wire between the central unit and navigation unit inside the navigation control module.






Got any clues as to what this means? Where is that control module?