As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE PILOT REPORTED A GENERATOR LIGHT DURING ENGINE START. HE ATTEMPTED TO RESET THE GENERATOR WITH NO SUCCESS. DURING SUBSEQUENT TROUBLESHOOTING THE MECHANIC FOUND THE STARTER/GENERATOR DRIVESHAFT SHEARED. THE STARTED/GENERATOR WAS REPLACED WITH A SERVICEABLE STARTER/GENERATOR.