I have hesitated to post as long as possible considering all the resources from others that have had issues with the evap system on JK's but i am stumped.

A couple months ago I bought an 154k mile 07 Wrangler X that I knew had the gascap warning on the dash, naively I figured a new cap would fix it. I scanned it when I got it home and it gave me P0457. I started to investigate and swap out parts chasing the 0457, at one point 0456 came up too. I thought I had it beat but now p0440 popped up.

Here is what I have done so far...
Tried an aftermarket cap
Leak Detection Pump (standard motor products) (fixed my issue with the gas pump shutting off with anything over a trickle)
Replaced purge solenoid (autozone brand) even though old one seemed to test good.
I checked the tubes by the battery and they had rub marks but I couldn't see a hole but I taped them anyway
Replaced fuel filler neck with good used (old one was nasty corroded) and bubble tested it in my pool to be sure
correct oe Mopar fuel cap in place of the aftermarket one
I smoke tested it with the leak detection pump vent capped off, nothing
With the same vent capped I pulled 3.5in/hg vacuum at the purge solenoid and it held

I am aware a fitting on the top of the tank can fracture but I checked that area a bunch during the smoke test, putting some pressure on the plastic to see it I could open up a crack and nothing. And the vacuum test supports it being good also.

What am I missing?

I ordered a new charcoal canister thinking perhaps the charcoal inside has broken free and clogged the system. Dunno where to turn after that.....

Does a breakdown exist with more detail on what the variety of evap codes mean?

 

i had to replace a Mopar 4861962AA Evap System Integrity Module Detector. And, yes I went replacing MOPAR gas cap also, but turned out it wasn't the cause.

I took a day to clear the code.

Mopar 4861962AA Evap System Integrity Module Detector for 07-21 Jeep Wrangler JL & JK and 07-17 Compass and Patriot MK | Quadratec

 

If the new charcoal canister doesn't come with a new evap system monitor switch attached, I'd get one and replace them together. Same as thunderstrike above recommended... Different names for the same thing, hate when they do that.

 

Early on I replaced the ESIM with a Standard Ignition LDP14. I noticed that it had components loose inside like a shuttle valve. I could see parts sliding back and forth when I tipped the unit back and forth. The one I took off did not have any movement inside, a the time I thought the old one was seized or something.

When I bought the charcoal canister recently I also bought a Dorman 310-215 ESIM/detection pump but it arrived late so I swapped the canister and reused the Standard ESIM. I got away with a few days of driving until yesterday AM when P0440 popped back up.

I decided to slap the new Dorman one on but noticed it was of different construction. No moving parts inside, almost like the original. Seems odd that even aftermarket parts would be so much different in construction/design. Maybe one was misboxed.

I am moving in the right direction however, I got the gascap message to disappear and the P0457 that would immediately pop up when I started the Jeep doesn't happen, just this P0440 after a number of trips. Maybe the Dorman ESIM will do the trick.

 

With the new ESIM, I got a couple of days DTC free then it popped up this AM. I think I am just going to top the tank off and keep it topped off (I read the evap system won't test until 3/4 of a tank or lower), drive it a few times to get all the other monitors ready then have it smogged. I'm allowed 1 monitor not ready. Assuming I get a passing test, I'll live with it until next season.

It think I may need to drop the tank but this Jeep is plagued with ground issues. I may trace the ground mentioned above and re-establish it and see what happens.

 

I ended up biting the bullet and pulling the tank to look for leaks at the fittings up top. I vacuum tested the line from the purge solenoid to the tank and it was fine. I vacuum and smoke tested the tank assembly and it was fine. I checked the used filler neck I installed and noticed the cap seal surface had 2 little gouges like it was nicked with a grinder or cutoff tool when it was extracted at the junkyard. I took some emery paper and worked it for a while until it was sanded out and cleaned and polished the entire sealing lip. I took an aftermarket cap and blocked the checkvalve (which opens under a certain amount of vacuum) and pumped the whole system down to 4 in/hg and it stayed put. Although I wish I noticed the gouges and addressed them first instead of fighting the tank R&R, if the system is fixed and the code doesn't come back I don't care.

Fingers crossed.

 

Did it solve the problem?

 

No. Ultimately selling it fixed the problem permanently.

 

☹ sad......

 

I had a similar issue. Turned out to be a hole in the line above the fuel tank. Used a smoker machine to find that one.