01 Sonata trouble codes

I have an 01 V6 Sonata that is experiencing the following trouble codes. P 0442 (evaporative emission control system leak, small leak) and P 0455 (evaporative emission control system leak, gross leak)
What are the odds of this being a problem with the gas cap? I have cleared the ECM of all trouble codes and will give it another try. I have been told to check the lines going to the charcoal canister as well. Just glancing under the hood, the canister isn't visible. Where is it located?
Thanks
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These codes could well have been stored by an improperly installed gas cap. The system will most likely test itself again as you drive the vehicle. If the lamp doesn't come back in a week, it was probably just the gas cap installation.
The canister is under the car at the left rear. You're not likely to see anything of significance visually. In a few instances, I've seen intermittent failures of the canister close valve to seal.
Let it ride and see what happens. It won't affect your performance and presents no hazard of deeper issues. If the light comes back, then I'd recommend taking it in and having it checked.
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I have a 2001 XG & got the similar codes late last Winter. After resetting the code a couple of times & getting the same thing a week to 10 days later, I finally took apart the canister assembly behind the lt. rear wheel. Turns out it was TOTALLY encapsulated in mud from our back booneys roads out here in the mountains. I cleaned everything off & since there's no dealer near me I even blew out the little replaceable filter (which I should have replaced). It's worked fine since but next time I get that code I will order in the filter. BC in BC

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Typically a P0449 or P0446 will set if the canister filter is clogged. This occurs because the system cannot suck in fresh air as designed.
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How do you test for trouble codes?
hyundaitech wrote:

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You need an OBD-II compatible code reader for cars 1996 and newer. Older cars have variousl methods depending on make and model.
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