Pierce Manufacturing is recalling certain model year 2012-2013 Arrow XT and Velocity emergency vehicles, manufactured January 1, 2012, through June 14, 2013 and equipped with quarter-turn ball valves installed between the glad hands connectors and the parking brake system. If the ball valves are left in the closed position, air pressure can build up on the parking brake circuit side and prevent the application of the spring park brakes when the parking brake valve is activated in the cab.