So got the P0442 on a 04 Dakota 4x4 4.7 auto 116 k. Gas cap just replaced with new Mopar cap. The filler tube is new.
I checked the line from intake to the solenoid (behind headlight/battery) no cracks or leaks. The line from solenoid to the canister don't see any cracks/breaks.
The solenoid i checked and and blow or suck any air through it. Tested with 12v and it seems to be working. The canister looks ok. The line from tank to canister looks good with no cracks/splits. The only thing i haven't got to yet is the air pump near the canister. I will remove and try 12v to that. The hoses all look good and there is no green T-fitting inline near the engine bay. Checked that first lol.

Also might add the lady who owns truck had it smoke tested and guess they didn't find any leaks?
Inspection is due and it will not pass here with the cel on. So need to get this fixed asap. Any in site is appreciated

 

You really have to squeeze the hoses along every inch as you check. Sometimes a crack can hide. I found and fixed cracks in my lines and the code would only appear once a year or so. Finally went away completely when I replaced the LDP which is underneath the truck, below the driver's seat for a quad cab. not sure on other models.

 

Welp still got a P0442 code. New Mopar fuel cap/ the fuel neck was replaced and is not rusty. The leak detection pump is new along with the 2 U shaped hoses. other hoses look and feel fine. The purge valve up near the battery is good as i tested it. I don't know what to do next the po had it smoke tested and they found nothing. I may do a quick diy transfer pump with cigar test but i don't think it will show anything. Also the truck idles fine and i checked all vacuum hoses. Does anyone know if before the purge valve there's a one way check valve or no?

 

I assume you cleared the code since doing all the work and it keeps returning, right? (Cause it won't disappear on its own) Also reset PCM.

 

On mine, the hoses that run under the battery tray were all coming apart. Had to physically remove the tray and PDC to see/service them.

As DV said, the evap codes are not self-clearing. You will need to clear the PCM, then have the fuel tank between 1/4 and 3/4 for the LDP to run.

Or, do like i did for a long time around inspection month, and just keep the fuel tank empty/full enough after a code reset that the LDP will not run, but all other emissions monitors will set. You get used to the light being on (although the root issue ought to be repaired regardless)