As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED NORMAL TAKEOFF AND DEPARTURE OF DAY, VFR FLIGHT. PASSING 17000 FT ± CARGO DOOR WARNING LIGHT CAME ON. CANCELED HORN, PERFORMED THE CHECKLIST, DECLARED EMERGENCY, RETURNED TO DEPARTURE. LIGHT EXTINGUISHED PASSING 15000 FT ON DESCENT. MAINTENANCE INSPECTED AND OPERATED CARGO DOOR. NO DEFECTS NOTED IAW CARGO DOOR, MM 52-30-01. RAN ACFT AND PRESSURIZED TO 8.5 PSI. CARGO DOOR INDICATION DID NOT FAIL. SYS CHECKS GOOD IAW MM 52-30. ACFT RETURNED TO SERVICE.