What was found
AIRCRAFT WAS GROUNDED. SHORTLY AFTER TAKE OFF WE RECEIVED ECAM LANDING GEAR DOOR NOT CLOSED. RECYCLED GEAR HANDLE AS PER ECAM TO NORMAL GEAR UP. REPLACED SENSOR (LMLG) 23GA PER MM 32-31-73-400, ADJ. PER MM 32-31-73-820, ACCOMPLISHED FUNCTIONAL TEST OF EXTENSION & RETRACTION PER 32-31-00-720. (NO FAULTS NOTED).