As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING APPROACH INTO DTW, THE LEFT MAIN LANDING GEAR DOOR DID NOT INDICATE LOCKED AFTER LANDING GEAR EXTENSION. PERFORMED COCKPIT OPERATING MANUAL PROCEDURES AND CYCLED LANDING GEAR. ALL INDICATIONS NORMAL AND THE AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE MAIN LANDING GEAR DOOR PROXIMITY SENSORS, 27GA AND 29GA. OPERATIONAL CHECK OK.