As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENGINE GENERATOR LIGHT ILLUMINATED PRIOR TO ETOPS ENTRY POINT. DISCONNECTED GENERATOR AND STARTED APU. FLIGHT RETURNED TO SFO. REPLACED NR 1 INTEGRATED DRIVE GENERATOR, OPS CHECKED NORMAL. SHOP FINDINGS: METAL FOUND IN FILTER, HYDRAULIC LOG FAILURE.