As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHX - AIR TURNBACK - FLT - 0590 - AFTER TAKEOFF FROM PHX EN ROUTE TO MCI WHEN LANDING GEAR WAS RETRACTED THE LT MAIN LANDING GEAR UNSAFE LIGHT ILLUMINATED. RETURNED TO PHX AND LANDED SAFELY. MAINTENANCE TROUBLESHOT AND REPLACED THE LT MAIN LANDING GEAR UPLOCK SENSOR/CONNECTOR IAW BMM 32-61-21-4, SENSOR ADJUSTED IAW BMM 32-61-21-5, OPERATIONAL CHECK WAS GOOD IAW BMM 32-61-00 PG 501-504.