As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DEPARTING, THE CREW OBSERVED AN UNSAFE(RED) WARNING ON NR 2 MAIN LANDING GEAR AFTER RETRACTION WAS SELECTED. THE CREW RETURNED TO POINT OF DEPARTURE AND AND CARRIED OUT A NORMAL CONFIGURATION LANDING. MAINTENANCE DETERMINED THAT THE UNSAFE CONDITION INDICATION WAS FALSE DUE TO A FAILED UPLOCK BOX. THE NR 2 MAIN GEAR UPLOCK BOX WAS REPLACED, TESTED SERVICEABLE AND AIRCRAFT RETURNED TO SERVICE.(TC NR 20060328004)