I keep getting the 455 and 442 codes for evap. So far I have done the following:

change gas neck and hoses (mopar parts)
changed gas cap (mopar part)
change both canisters, boot, and hoses that connect to it (aftermarket dorman)
vacuum tested the canisters to make sure they held vacuum
changed the purge valve (yes it was installed correctly) (mopar part)
checked all visible hoses and lines for splits and did not see anything

This truck was taken off the road back in 2011 for failing inspection with these codes and up till now I still can't figure out what is wrong with it. Even spent a ton at mechanics to get them to fix it and all they did was reset the computer and tell me to drive it for the drive cycle.

So, if anyone knows anything else that may cause it please let me know.

 

P0455 Evap Leak Monitor Large Leak Detected
P0442 Evap Leak Monitor Medium (0.040) Leak Detected

Did you check the hose that comes off the the throttle body?

 

Checked it today and it was in perfect shape

 

Have anyone around that can smoke test it?

 

You can also use a cigar like I do, if you smoke

 

I just found our today that the gas fuel neck and actually for a 99 Dodge ram 1500 and takes the threaded gas cap which it has. Would using a 99 fuel neck on a 2001 cause the code to be thrown?

 

Only if there is a leak.

 

Finally got someone to smoke test it. There was a ton of smoke coming out of the vent thing under the hood and a little bit coming out from gas cap area. Changed the gas cap with 2 different brands of non-vented gas caps and there was still a tiny bit of smoke coming from it which makes me think the neck is leaking where the threaded part of the neck is attached to the rest of the tubing. Other than that there was some smoke coming through the intake, but was told that was normal.

 

There may be a sensor on the fuel tank that has gone bad called the fuel tank pressure sensor.

 

In a smoke test is the smoke introduced into the test port were there is a 1 psi maximum warning after first removing the schrader valve?