If it's only with the key in on position & the car doesn't have to be started to hear it it's prob. the small fan running in the relay control compartment under the hood next to the battery. This fan is a continuous run with the key on & in run pos. to keep the same box cool & also cools, via small duct work, the tranny control module if equipped with an auto. tranny & the radio amplifier which are located under the pass. floor.