Daimler Trucks North America LLC (DTNA) is recalling certain model year 2013 Freightliner Business Class M2 vehicles manufactured May 29, 2012, to June 11, 2012, and equipped with certain compressed natural gas (CNG) fuel tank systems manufactured by Agility Fuel Systems. In the affected fuel systems, due to a separation of the valve seat from the valve stem, the manual tank shutoff valve can get internally stuck in the closed position while being opened, although the knob may indicate that the valve is open.