Jeep is a 2010.

P0456 never clears permanent and keeps triggering the CEL.

Replaced so far -
Gas cap. OEM. Twice. P0456 CEL comes back on after about 24 hours.
Leak detection pump. OEM. Twice. Also replaced with the flat-edge gasket. P0456 CEL comes back on after about 24 hours.
Charcoal canister. P0456 CEL came back on after about 24 hours.
Purge valve. P0456 CEL came back on after about a week, Permanent code never cleared.

No abnormal smoke from a smoke test. Checked the fuel tank - it was replaced shortly after I purchased the Jeep in 2013. It doesn't appear to be damaged.

All visible hoses appear to be intact and in good condition with no visible wearthrough or cracking.

I've been fighting this for 6 months now and I have to SMOG this thing. I'm running out of ideas, I'm out of time and I have nothing left to replace..

What am I missing?

 

I think the only thing left is the Evaporative System Integrity Module (ESIM).

 

If that's the white box on the back of the charcoal canister, unfortunately I've already replaced that twice. That's the part they also call the "leak detection pump". I replaced both it and the O-ring, and I used the OEM O-ring with the flat faces.

 

considering the tank was replaced, the only thing that really comes to mind is maybe you have a crack at one of the nipples that resides on top of the tank, and that a smoke test does not show itself there easily considering it's such a tight spot to view. Can't imagine that there is an actual blockage of any line, and you have replaced about everything else.