Check Engine Light 99 Sonata

Hello,
I keep getting a check engine light (usually about the time when the gas light is going to turn on) and it comes back with codes: p0442 and/or
p0455 (both for evap issues).
I spoke to someone with a 01 sonata and they had the same problem but had it fixed under warranty and don't remember what the trouble was...
I know there are no drivabilty issues with these codes but, it is getting annoying having to reset them all the time.
What is USUALLY the problem and where should I look... I don't want to take it in if I don't have to because they will charge an arm and leg to just "diagnose" the problem even after I tell them what the codes are.
Thanks for any help
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
BTW,
I did install a new gas cap that I bought from the dealer.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If you're getting both the P0442 and P0455, the number one problem would be the canister close valve. But realistically, the problem could be anywhere in the evap system. Pay for diag vs. pay for close valve that may not fix the problem-- pay your money; take your chances.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.