What was found
DEN - DURING CLIMBOUT, THE LEFT MAIN LANDING GEAR DOOR INDICATED IN TRANSIT AFTER LANDING GEAR WAS RETRACTED. CYCLED LANDING GEAR HANDLE AND ALL INDICATIONS WERE NORMAL. AIRCRAFT CONTINUED TO DTW WHERE AN UNEVENTFUL LANDING WAS ACCOMPLISHED. MAINTENANCE FOUND THE LEFT MAIN LANDING GEAR DOOR PROXIMITY SENSOR (27GA), TARGET LOOSE. TIGHTENED SAME AND ALL INDICATIONS WERE NORMAL.