As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DC GENERATOR CAUTION LIGHT ILLUMINATED SHORTLY AFTER TAKEOFF. COULD NOT RESET. AIR RETURN TO DTW. MAINTENANCE REPLACED RT DC GCU (P/N 51539-007B) (S/N ON 99572). RT AIRCRAFT IN SEVERAL CONFIGUATIONS. ALL CHECKS GOOD AT THIS TIME. ALL IAW SF340 AMM.