As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MASTER WARNING CHECK FIRE DET AND APU FAULT LIGHT ILLUMINATED DURING FLIGHT AT CRUISE. LIGHTS REMAINED ILLUMINATED TO LANDING. DIVERTED. LANDING UNEVENTFUL. REMOVED FROM SERVICE. INSPECTED APU FIRE LOOP, NO DEFECTS FOUND. R&R'D FIRE PROTECTION PANEL IAW Q400 AMM 26-00-01-000/400-801 AS PRECAUTIONARY MEASURES. SYSTEM OPS CKS GOOD. RETURNED TO SERVICE.