Sat nav was working fine, wife cleaning behind passenger seat and disturbed the retro fitted multimedia Video Interface Unit, now have "no nav available" message on screen. Have run 753 diagnostic and it reports DTC U1A0131 GVIF Signal Fault.
Having looked at the jumble of wiring (by previous owner), it looks as though the factory nav system doesn't run through the MM Interface unit, so what is the problem with the system? Have disconnected and reconnected connectors to rear of nav DVD drive but no change, system dials register the nav DVD but cannot initiate the nav system. Help!

Check the GVIF IN OUT connectors.

Do NOT turn Them upside down else further confusion!

It doesn't look possible to insert the connector upside down?, I disconnected it and reinserted it the same way.

The other end of that black cable.

Check its plugged in.

Does your DVD player, or whatever you use that GVIF for display on the screen still ?

The blue connector that goes into the rear of the nav unit itself can go in upside down if you disturbed that one as well

The no nav message appeared before I removed any of the connectors, was working fine before the MM interface unit was disturbed.

Did you fix the problem. Mine says exactly the same after removing my Radio and touching the interface box.