Fiesta 2009 Audio Test Menu

[Christopher]

Please can anyone help.
My Audio system (Fiesta 2009 MK7 - without phone) has greatly reduced volume.
There do not appear to be any external Faults with wiring or speakers.
I have accessed a "test" menu for the audio system ("OK" for a few secs, then turn key to pos. 2) but cannot seem to find any reference to what the parameters mean. Anyone got any clues??

I am trying to find out if the head unit is faulty or whether there is some Firmware issue.

If the head unit is faulty, is it simply a matter of plugging a replacement in, or does it have to be matched to the VIN number? If so how is this achieved??

Many thanks in advance.
Chris