The evap canister looks like a small black shoe box with another small box with2 pipes attached to it. The smaller black box is the perge valve. On mine this purge Valve is what failed. It would give me the gas cap warning and throw the code. It was about $26 I think and is easy to replace. I am out of the country right now but if you still have the issue I a week, and no one else has been able to help I will post a YouTube video on how to replace it.
Dave

 

Further back. The evaporative canister is towards the back of the Jeep. I'd take a picture of mine, but it's been moved from stock, so wouldn't help. Anyway, it's 3:10 in the morning. But, look towards the back. It has a couple vacuum lines connected to it. It's about the size of a very small shoe box (like a child's shoes might come in).

 

Ah-hah! Here's a picture of one. This one has been relocated, but that's what it looks like ...

 

Thank you so much I'll check there here in a bit )))

 

I thought mine was white or off white. Hmmm, I'll need to look when I get home. Senior moment...maybe