As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
R GEN DRIVE EICAS MESSAGE. AIRCRAFT BACK TO BLOCK AND GROUNDED BY MAINTENANCE. MAINTENANCE. RECONNECTED DRIVE. VERIFIED PROPER OIL SERVICE. VERIFIED IDG CHARGE PRESSURE SWITCH OPERATION. REPLACED GCU, REF B767 AMM 24-22-02. RAN ENGINE. ALL GENERATOR FUNCTIONS AND INDICATIONS NORMAL.