GMC YUKON TROUBLE CODE

01 6.0 In A Yukon Xl. Cyl #2 Misfiring. Parts Changed/checked ; Head Gaskets, With Valve Job. Coil. Plug Wire. Plug. Injector. Fuel Psi Reg...

What Does It Mean When The Repair Code Is P0440? What Should I Fix? Thanks, Sherry

I Am Getting A Trouble Code P0440 And P0440pd, I Look In The Reference Code Book For The Description But It Just Says Evap Emission...