What was found
THE LT MLG RED UNSAFE LIGHT REMAINED ILLUMINATED AFTER TAKEOFF. THE GEAR WAS CYCLED, BUT THE LIGHT REMAINED ILLUMINATED. WHEN GEAR WAS EXTENDED ALL THREE GREEN LIGHTS ILLUMINATED WITH NO RED LIGHT. THE AIRCRAFT LANDED AT IAH WITHOUT INCIDENT. MAINTENANCE FOUND THE LEFT MLG UPLOCK SENSOR AT FAULT. THE LT UPLOCK SENSOR WAS REPLACED. IN ADDITION, THE M988 CARD WAS REPLACED AS A PRECAUTIONARY MEASURE, OPERATIONAL CHECKS WERE GOOD IAW MM 32-09-01.