why is there a whirring noise in my 2005 Honda Fit vehicle when I turn the engine off

Hello, You are probably hearing your engine cooling fan running/slowing down as you turn off the engine. You can fact check this by opening the hood when the vehicle is being turned off, and watch the cooling fan while listening to the noise. The speed of the cooling fan should correlate with the noise volume and pitch. The clicking noise when you reverse is could be one of many things, and I suggest having the issue investigated. Sorry, there just isn't much to go on without hearing the noise or pinpointing the location.