What was found
UPON SELECTING FLAPS 25 RECEIVED A TE FLAP DISAGREE EICAS. FLAP HANDLE WAS AT 25 BUT THE FLAPS WERE AT 20. RAN QRH, RETRACTED FLAPS TO UP USING ALT FLAPS AND DIVERTED TO HNL. UNEVENTFUL FLAPS 20 LANDING USING ALT FLAPS. EMERGENCY DECLARED. INTERROGATED FLAP/SLAT SYSTEM, FOUND #2 FLAP SLAT ELECTRONIC UNIT ASSEMBLY FAULTING DATA LINK INOP. SWAPPED ELECTRONIC UNIT TO #3 POSITION AND FAULT FOLLOWED. REMOVED AND REPLACED FLAP SLAT ELECTRONIC UNIT PER M.M. 27-51-01-2, ALL CHECK NORMAL. CYCLED FLAPS/SLATS UP AND DOWN MULTIPLE TIMES, ALL CHECK NORMAL.