2011 Chevrolet 2500 HD 6.0L with P0496 engine code

Question

Only act up when filling up with gas. And also with code P0442. Engine will crank over a lot and when it stars it run rough for a while. Turns on check engine lamp and the it stays on.
Then it runs fine till you refill with gas.

Answer 1

P0496 Evaporative emission system flow during non-purge

P0442 Evaporative emission small leak detected

P0496 and P0442 are class as B type codes , they will not cause a rough idle and the engine to crank over alot.Something else is causing this situation When P0496 occurs this is from the FTP (fuel tank pressure) sensor monitoring fuel tank pressure.The FTP can be giving false pressure reading and this will not cause rough or hard starting conditions.These 2 codes can suspends the rough idle start up  codes till this situation is resolved.. There is also a Recall for the TPS (throttle psoition sensor) TSB # 11273A