As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT, ACCESS BUSS CAUTION MESSAGE. BUSS 1 & ENG 1 DISPLAYED AS MAGENTA ON SYNOPTIC PAGE. AFTER AOM1 CHECKLIST FAILED TO RESTORE FAILED SYS, APU WAS STARTED RESULTING IN PARTIAL RECOVERY OF LOST SYS, BUT NO FLOW BARS CONNECTING BUS 1 OR ESS BUS EVEN THOUGH ESS BUS APPEARED GREEN. R & R LT IDG GCU IAW AMM 24-11-07. OPERATIONS CHECKED GOOD.