P0455 code question for the experts.

P0455 - Major Evap System Leak on a 01 4.0 XJ. Got to love this emissions stuff!

Does anyone know how quickly this code will return after being cleared? Will it come back right away if not corrected or does it have to run through a certain number of cycles before returning?

Mine will return in 2 or 3 days and I'm trying to figure out if it's an intermittent problem or if it just takes that long for the PCM to cycle the CIL back on.

The PCM is programmed to run the EVAP leak test only under certain conditions....For the LDP EVAP leak test to run, the vehicle must be cold, and the fuel level must be between 15 and 85%.
SO ...depending on how much fuel you have in your tank, will depend on when the next time the test will run....if you meet the fuel condition, it will probably be a minute or two after you start the vehicle up cold.

you can read this article for more details...

http://www.aeswave.com/images/Products/atts-16%20sample.pdf

In speaking with a Dealership mechanic that fixes these evap leaks all the time, he told me that most leaks are from cracked rubber lines that connect the hard plastic evap lines ...there are evap lines that run down the firewall as hard plastic, then become rubber as they go under the body, then change back to hard plastic... they fail there often, and back at the connections to the evap can itself. Sometimes a bad gas cap, gas tank leak, or gas tank vent tube leak. So inspect the lines inch by inch, end to end with a high intensity light...if you squeeze the rubber sections, you will probably crack a hose if it is ready to go, or make it worse if it is cracked allready! I am also pretty sure the PCM won't set the CEL on the first failure...so it will probably fail test 3 times with the right fuel conditions at cold start, before CEL light sets.

Found the problem I think. A did a close inspection of all the lines with a mirror and flashlight and found a cracked hose on the smaller line right where it goes by the exhaust manifold. Guess the heat got the best of it. I'm replacing all the straight hoses this weekend and bought an OEM gas cap. All the specialty hoses look good for now.

Hopefully this will end the CIL.