What was found
CRUISING AT FL390 "FADEC 2" LIGHT ILLUMINATED ON MWP FOLLOWED IMMEDIATELY BY A ROLL BACK TO FLIGHT IDLE OF NR 2 ENGINE. CREW COMPLETED CHECKLIST ITEMS. EIED 2 DISPLAYED A "F2A WF SOFT FAULT". ENGINE 2 REMAINED AT FLIGHT IDLE FOR ABOUT 20 MINS. DURING DESCENT AT ABOUT 14000' ENGINE RESUMED APPARENT NORMAL THRUST AND OPERATION. AFTER LANDING EIED 2 DISPLAYED MSG LISTED ABOVE AND "F2A OTHER FADEC NOT CAPABLE" AND "F2A FADEC BIT FAULT" AND "F2B WF POSITION FAULT". R & R NR 2 ENGINE HMU WITH AN O/H UNIT IAW LMM 73-20-01. COMPLIED WITH OPS & LEAK CHECKED IAW LMM 72-00-00.