Eh, that sounds fishy to me. Thats why if I was ever asked to step out of my car, I would lock my doors.

I thought it was an amendment, like the right to remain silent, the right to not consent to searches without a warrant (not necessarily called that though)

I really don't think smell would be considered probable cause though, there is no way to prove a smell really. If you see something, thats different.

Edit: http://youtube.com/watch?v=3NmC5wHfCdM I don't remember the guy saying anything about smell.