As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROXIMATELY 2:30 INTO OUR FLIGHT AT FL 410. THE NR 2 TRANSFER BUS OFF LIGHT ILLUMINATED BRIEFLY THEN EXTINGUISHED. THIS HAPPENED IMMEDIATELY A SECOND TIME. WE ACCOMPLISHED QRH 6:11 TRANSFER BUS OFF. ONCE THE APU WAS ONLINE AND COVERING THE NR 2 TRANSFER BUS WE HAD NO MORE ISSUES. GROUNDED-YES. REMOVED & REPLACED NR 2 IDG, REF B737-800 AMM 24-11-11, ACCOMPLISHED OPERATIONS OF NR 2 ENGINE IDG, OPERATIONS CHECK GOOD, REF B737-800 AMM 24-11-00-700-803.