As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT MAIN LANDING GEAR UNSAFE LIGHT REMAINED ON AFTER GAR RETRACTION. FLIGHT WAS RETURNED TO DTW AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND LEVER ON LEFT MAIN GEAR UPLATCH NOT SECURE. SECURED LEVER. OPERATIONAL CHECK NORMAL. AIRCRAFT RETURNED TO SERVICE.