It checks resistances withing the given circuits.
To Enter Self test, make sure it is on Radio and then turn off.
For low series radio press and hold preset buttons 3 + 6 within 4 Secs of turning on( For high series radios press and hold preset 4 and TA button within 4 Secs ).
Release these buttons and it should enter self test displaying what circuit is being tested, if a fault is found then a fault code is displayed and a pinpoint test need be followed.
Fault codes can also be read off the radio using Fords IDS.
2010 Titanium 2.0 TDCI Panther Black.