After having no luck with replacing the gas cap (suggest getting cap from the dealer only), I inspected the connections around the charcoal canister (under the jeep / rear). A half turn (after holding in the lock clip) releases the hose and small black box connecting to the charcoal canister. I noticed a runner seal that appeared kinked. I pulled it off, cleaned everything up and added some silicone (o ring lubricant stuff) to keep the seal from drying out. Also unplugged the other connector on that line about a foot up the line and gave it the same clean up, silicone. lastly i removed the o ring on the gas gap (the new one) and added the silicone and re-installed. Reset the battery and its been quite a while now with no recurrence. I think the culprit was the connection to the charcoal canister. From what I recall, the computer does a test of the system every so many miles, that's why is will come on, or go off (if the condition is resolved) on it's own at some set interval. Good luck with your ghost in the machine!

 

Further to my prior post. reference this link:
Vapor Canister and Leak Detection Pump. Fits: WRANGLER 4x4, 3.6L V6 VVT, 5-Speed Auto W5A580 RUBICON, WRANGLER 4x4, 3.6L V6 VVT, 5-Speed Auto W5A580 SAHARA, WRANGLER 4x4... | FACTORY CHRYSLER PARTS
The oring is #3 (Canister seal). and the seals at both ends of part #1 (Hose. Canister to Natural vacuum leak detection).

 

What a poor design , but I still love my JK, I just put electrical tape on my hose near the batter, lets see if it works.

 

Anyone have pics of where the hole is? Got the same code (P0456) and can't find a hole. Most of the lines that run towards the battery look like wires

 

I have the same P0456 code. I checked the evap lines near the battery but they are good. The suspect line discussed in this thread doesn't even touch my battery all. I felt with my hand and line feels perfect. I first tried replacing the gas cap with a "Stant" cap. This didn't fix it. I then replaced the purge valve solenoid because it was pretty cheap, I put the original gas cap back on because I assume it is good, the seal looks good to me. This worked for a week or so, maybe it was the 200 miles mark, then the CEL came back on. So now, I am trying the new gas cap again. It's been 2 days with no light but I doubt I have it fixed yet.

Here are the things I checked
- gas cap seal - should be good, unless the Stant is not as good as OEM, original may be good as well
- filler neck seal - looks ok by inspection
- evap line at canister near rear of jeep - looks good by inspection
- purge valve - replaced, $15
- evap lines to and from purge valve - lines look, feel perfect

Has anyone else had any success with P0456 code? I have seen other posts where others have multiple codes like P0456,P0457 and "gas cap", I only have P0456. Maybe this can help isolate the problem. It would be nice to have a thread for posting trouble codes and successful fixes for each trouble code. Any ideas on where I should look next?

 

This worked for me. The crack on my hose was down the bottom next to the battery, close to the purge valve connection.

 

Ok, I went ahead and taped the evap line at the near the battery. It looks fine but I thought I would try it anyway, I did feel a slight "scuff" near the bend so I went ahead and taped it up. I also checked my evap canister pump and o-ring, all looked good so I am still looking for my "very small leak".

 

Try putting Vaseline around the seal on the gas cap. Worked for me.

 

Vaseline attacks some polymers over time. Pure silicone oring grease is a better alternative. Available in all pool supply stores.

 

Light back on. I am going to look again at the leak detection pump. It seems to be a common problem. Does anyone have any tips on running a smoke test?