If you are caught stealing cars in Arizona as a minor, you are facing potentially severe consequences. If you are within a couple of years of turning 18, there is a chance your case could be processed in adult court where the consequences are much more severe.
In Juvenile court the focus is rehabilitation. The adult court, however, focuses on punishment. Theft of a vehicle and/or theft from a vehicle are serious crimes in the state of Arizona. If you are convicted of these types of charges, you can expect to spend some time in jail.