As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE WARNING ILLUMINATED AT GATE FOR AFT CARGO. CARGO DOOR WAS OPEN AND EMPTY. REMOVED FROM SERVICE. CLEANED SMOKE DETECTORS IN AFT CARGO. PERFORMED OPS EST OF THE BAGGAGE SMOKE DETECTORS IAW Q400 AMM 26-12-06-710-801. OPS TEST GOOD. SMOKE WARNING STAYS OFF AFTER THE TEST. RETURNED TO SERVICE.