I have a similar condition with my EX Sorento. It just tells me that, even with closed circulation, the passenger cabin is not hermetically sealed. It could have been done on purpose - some vehicles do allow some fresh air in even when set to closed. Or it could simply be a fit and finish problem, meaning, the vents and seals do not fit perfectly and allow outside air to seep in. Mine is negligible and doesn't bother me, though.