As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EICAS MSG (L,R) UTIL BUSS OFF DISPLAYED. UTILITY BUSS OFF LGT ILLUM. SYS FAILED TO RESET. BUSS PCU FAILURE. REPLACED BUSS POWER CONTROL UNIT.TESTS OKAY. RAN BOTH ENGINES & RAN ALL ELECTRICAL POWER SYSTEMS USING ALT BUSSES ALL INDICATION & OPS NORMAL.