As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHX - DEN - ATB - FLT 490 - DURING CLIMB CREW SELECTED GEAR UP. RED RIGHT MAIN LANDING GEAR LIGHT REMAINED ILLUMINATED. PER QRH CREW SELECTED GEAR DOWN. THREE GREEN GEAR DOWN LIGHTS ILLUMINATED. CREW DECLARED AN EMERGENCY AND CABIN WAS PREPPED. THE CREW RETURNED TO PHX. THE LANDING WAS UNEVENTFUL AND THE A/C TAXIED TO THE GATE. MX DISCOVERED THE RIGHT MLG UPLOCK SENSOR WAS OUT OF ADJUSTMENT. MX ADJUSTED SENSOR. OPERATIONAL CHECK WAS GOOD. THE A/C WAS RETURNED TO SERVICE.