i failed the emission test the other day here in IL.. any one know what the code P0455 EVAP control system leak detected means? and what i need to replace to fix it? thanks

Might just be a leaky gas cap.

HX44 DTC P0455: VISUAL INSPECTION FOR SUBSTANTIAL EVAPORATIVE EMISSION SYSTEM LEAKS

Continuous Memory Diagnostic Trouble Code (DTC) P0455 indicates that the Evaporative Emission (EVAP) control system detected a large leak or no purge flow.

Possible causes:

After market parts and accessories nonconforming to the EVAP system specifications.
Damaged, missing or improperly installed fuel filler cap.
Blockage in fuel vapor hoses/tubes (EVAP canister tube, EVAP canister purge outlet tube or EVAP return tube) in EVAP system.
Disconnected or cracked fuel vapor hoses/tubes in EVAP system.
EVAP canister purge valve stuck closed.
Canister vent (CV) solenoid stuck open.
Fuel tank pressure (FTP) sensor malfunction.
EVAP canister leaking.
Fuel vapor control valve tube assembly blocked.
Fuel vapor vent valve assembly blocked.
Check for missing fuel filler cap. If the cap is loose DO NOT DISTURB EVAP system.
Verify that both the input port vacuum hose and EVAP return tube are attached to the EVAP canister purge valve.
Note: If the EVAP canister-CV solenoid assembly is not accessible to perform the following step, Go to the Powertrain/Engine Group, Evaporative Emissions Section in the Workshop Manual for removal and installation procedures.

Verify that the CV solenoid is properly seated on the EVAP canister (if possible).
Visually inspect for disconnected or cracked fuel vapor hoses/tubes between the intake manifold, the EVAP canister purge valve, the EVAP canister, the fuel vapor vent valve assembly and if applicable the fuel vapor control valve tube assembly.
Check for damage to the fuel filler pipe and the fuel tank.

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_______________________DogDomain_______________________

darn Dog_Party gots skills.

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That is a very common failure here in Cali and most shops will warn you on the pre-test and sell you a new cap.

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71 C101
04 KJ
03 SFA KJ Sport
LOST JEEPS So-Cal

In IL we don't have inspections or pre-tests.

The way it works here is after the vehicle is 3 yrs old or something similar, you get a card in the mail and go to the testing facility (there is no charge for the test)

If you fail, they give you 90 days or some such to fix the problem and show up for a second test.

As a plus, if you live in a rural area, they don't even require the test. It's only for the urban areas.

BTW, I bet the others are right - leaky gas cap, or if you have good luck, it might have just been seated wrong and the tester was too lazy to reseat it for you.

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2008 Unlimited Rubicon - 3.5" AEV/Nth lift - 35" MT/R with Kevlar - AEV Wheels - York OBA
2008 Patriot - Fuel Saver

it says on the sheet of paper that the gas cap test passed.. what should i look for here.. where is the evap located.. just for info i have had the o2 sensor replaced about a year and half ago.. it could possibly be the tank pressure.. cuz my jeep just sitts in the drive way a couple days at a time during the summer because i have a motorcycle that i love to ride when its nice out.. but i have put gas in numerous times since i started having the trouble light on in my dash..

im glad that i live in northern az, small town not city so they dont do emmisions test here which is good for me because i cut out the cat. and welded a straight pipe, then i put a magna flow muffler. now the kj runs like a champ

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Thomas Tusser

Sorry it's not the fuel cap KJ Juice. That was the easiest possibility from the list.

You might have to go through that whole list of possible causes that I gave you. But I think my next steps would be:

Verify that both the input port vacuum hose and EVAP return tube are attached to the EVAP canister purge valve.

Visually inspect for disconnected or cracked fuel vapor hoses/tubes between the intake manifold, the EVAP canister purge valve, the EVAP canister, the fuel vapor vent valve assembly and if applicable the fuel vapor control valve tube assembly.

Check for damage to the fuel filler pipe and the fuel tank.

What year is your KJ? Do you wheel? Got a fuel tank skid? Or it could be a cracked/failed hose. I don't have any more detail to help with because I have the diesel, so I don't know your Evaporative Emission (EVAP) control system worth a PBBBBT.

Good luck man.

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_______________________DogDomain_______________________

I had the same code. Replaced the gas cap and several hoses that the
-25 degree weather had cracked. Two of the hoses were on the intake and one was underneath the vehicle and was a vacum hose for the fuel system. I don't know exactly which one fixed it but the code never came back.

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When I moved to CO I had my KJ emission tested and it passed with flying colars,the bad emissions where so low they tested again and still didn't believe it so they had there machine recalibrated and tested a third time with the same results.Just proves really good routine maintance really does pay off.The main evape canister is located in front of the gas tank with lines running all the way to the engine bay,they have tests to check for evap leaks in these line not sure how much they will charge you though.