Violation of the Fourth Amendment: For a law enforcement officer to legally search your vehicle they must have a search warrant or probable cause to suggest you have broken the law. Probable cause must be based on witness information, the officer’s sense of smell, sight, and hearing, or some other valid evidence. If the officer did not have a legitimate reason to search you or your vehicle you could argue that they were operating in violation of your Fourth Amendment rights.
Illegal traffic stop: Police officers are required to have probable cause before making a traffic stop. This means that they must have evidence or a legitimate reason to believe that you are breaking the law in order to legally pull you over. If the officer did not have a valid reason for the stop then you may be able to prevent them from using any evidence obtained during the illegal stop.