As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
L GEN DRIVE , L GEN "OFF" EICAS MESSAGE. AIRCRAFT BTB AND GROUNDED BY MAINTENANCE. PERFORMED BPCU BITE IAW B767 FIM 24-20 FAULT TREE 01 AND TASK 24-20 804. RECONNECTED IDG AND RAN ENG. COULD NOT DUPLICATE NO FAULTS FOUND. PLACARD REMOVED. MX PROC C/W. AIRCRAFT RETURNED TO SERVICE.