What was found
WHEN TAXIING FOR TAKEOFF, A LEFT OUTBOARD BRAKE TEMPERATURE WARNING LIGHT ILLUMINATED. THE CREW RETURNED TO THE GATE AND MAINTENANCE WAS CALLED OUT TO THE AIRCRAFT. MAINTENANCE INSPECTED THE LEFT BRAKE AND FOUND THE BRAKE TO BE NORMAL. MAINTENANCE DEFERRED THE LEFT BRAKE TEMP INDICATION PER MEL. LATER MAINTENANCE TROUBLESHOT AND CLEANED THE LEFT TEMP SENSOR. THE MEL WAS CLEARED AND THE AIRCRAFT RETURNED TO SERVICE.