Trouble shoot a engine code

I have a 2003 Dodge Ram 1500 4.7
The code is PO440

I have been told it the gas cap. I just want make sure that is the problem. I already fix the canister tank one of the hose was cracked.

Please help!!! Just want to know if I'm doing the right thing.....

evap purge system performance......there can be many problems.....bad purge, open wire in the ldp switch, no vacuum at the ldp, etcccc....but I have replaced many of leak detection pumps to fix this problem...faulty switch inside of the pump...

Here's an interesting thread,

http://www.automotiveforums.com/vbulletin/showthread.php?t=953294&highlight=p0440