As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT AT FL400, WE EXPERIENCED A NR 2 ENGINE GENERATOR CONTROL UNIT "UNDER-VOLTAGE" INDICATION. THE SYSTEM AUTOMATICALLY COMPLETED A LOAD SHED OF NON-ESSENTIAL ITEMS. WE FOLLOWED THE CHECKLIST, STARTED THE APU, AND CONTINUED OUR TRIP TO THE DESTINATION. REPAIRS WERE MADE THE SAME DAY WITH A REPLACEMENT GCU.