Can you say no to a police dog searching your car if pulled over?

== == You can say no to a voluntary search, it is your right as an American citizen.

However if probable cause is found to conduct a search, or if you are being arrested for a violation or warrant then they can do it without consent.

The fourth Amendment gives you that right. here is more info from answers.com and Wikipedia The Fourth Amendment(Amendment IV) to the United States Constitution is one of the provisions included in the Bill of Rights. The Fourth Amendment guards against unreasonable searches and seizures, and was designed as a response to the controversial writs of assistance (a type of general search warrant), which were a significant factor behind the American Revolution. Toward that end, the amendment specifies that judicially sanctioned search and arrest warrants must be supported by probable cause and be limited in scope according to specific information supplied by a person (usually a peace officer) who has sworn by it and is therefore accountable to the issuing court. In Mapp v. Ohio, 367 U.S. 643 (1961) the Supreme Court ruled that the Fourth Amendment is applicable to the state governments by way of the Due Process Clause of the Fourteenth Amendment. The Supreme Court has said that some searches and seizures may violate the Fourth Amendment's reasonableness requirement even if a warrant is supported by probable cause and is limited in scope. Conversely, California courts have found that routine warrantless seizures are legitimate where an "officer has probable cause to believe that the person to be arrested has committed a felony, whether or not a felony, in fact, has been committed." The police dog itself can also be the one to find probable cause. If, for instance, you say no to the police officer or police dog searching inside your vehicle, the K-9 handler can have the dog "search" the air around your vehicle without your permission. If the K-9 alerts his handler that there are narcotics in your vehicle, then they would have probable cause to search the vehicle.