As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - FLT 894 - EN ROUTE PHL-FRA, THE CREW RECEIVED A FLICKERING EICAS MESSAGE ''L GEN DRIVE'' AND WARNING LIGHT. THE APU WAS STARTED, AND THE IDG WAS NOT DISCONNECTED. THE FLIGHT RETURNED TO PHL AND LANDED WITH NO FURTHER INCIDENT. MAINTENANCCE REPLACED THE LEFT GENERATOR CONTROL UNIT. (M)