As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED DUE TO CAPTAIN FLIGHT INSTRUMENT TRANSFER BUSS STATUS MESSAGE ILLUMINATED. EMERGENCY DECLARED, LANDING UNEVENTFUL. REPLACED CAPTAINS INSTRUMENT BUSS VOLTAGE SENSING UNIT. SYS CHECKED NORMAL. DISCREPANCY REPEATED 3/23 & 3/25. FOUND THE NEUTRAL LUG HARDWARE NOT PROPERLY TORQUED & LOOSE. SECURED INSTALLATION. PERFORMED ENGINE RUN & VERIFIED LT IDG OPERATED NORMALLY.