2006 express 2500 check engine light

2 codes p0442, p0442p, replaced gas cap, light came back, took gasket off aftermarket cap put on old cap took 250 miles to ready evap system. 2 days later light back on same codes. any ideas??

2 codes p0442, p0442p, replaced gas cap, light came back, took gasket off aftermarket cap put on old cap took 250 miles to ready evap system. 2 days later light back on same codes. any ideas??

You still have a small leak in your evap system.
Check all hoses and lines and valves and vents and filler neck for leaks.
Put a vacuum gauge or good scanner on system and watch for leak down.
Some repair shops and dealer have a smoke machine for hard to find leaks.
Good Luck