I am getting a P0442 trouble code on my 2002 Jeep Wrangler. I have replaced the gas cap and one kinked line. But i still ge the light about once a month. What can i do to fix it? i have had the jeep at a mechanics shop 3 times. It has been smoke tested with no leaks found. The gas cap and the filler neck have been replaced. What can i do to fix this problem?

A code P0442 most likely means one or more of the following has happened: A loose or improperly affixed gas cap A non-conforming gas cap (i.e. not factory/original brand) A small leak/hole in a fuel vapor hose/tube Other small leak in EVAP system Faulty vent o-ring seal Defective vent valve Defective purge valve Defective leak detection pump

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OBD-II Trouble Code: P0455 Evaporative Emission Control System Leak Detected (no purge flow or large leak)

Most people find it is from the gas filler cap. Here is a page where people discuss the problem and what they did:

http://www.jeepforum.com/forum/f9/engine-code-p0455-1051189/

I too have had the warning on the dash indicating: "GAS CAP". It is a generic code for anything to do with the fuel cap, filler hose, or overflow, including the charcoal cannister evaporative recovery system. Sometimes it is an easy fix, to simply replace the gas cap. If people consistently twist the cap past the point where it clicks, after closing = it can wear out the cap, and prevent a good seal. However, a large majority of people have overfilled their tank too many times and the evaporative cannister is full and the overflow line is clogged or kinked. Start with the cheap solution first, gas cap.
My problem started after running the extreme obstacle course at Daytona Beach Jeep Beach 2013 at which point I pulled the cannister off the bottom and had to replace it. There are no skid plates protecting it and it would be easy for sticks etc. to get jammed up in and around that cannister while even mildly off road. Crawl under and follow the filler hose down from the passenger rear of the vehicle. The charcoal cannister is approx the size of 2 loaves of bread and sits just forward of the axle, next to the drive shaft.
Good luck.

p0455-- emission control system ( a large leak ) the most common cause is a bad seal on fuel cap, remove and replace cap, if light stats on. replace cap. if not the cap it could be any where in emission system. p0442 is--same as above. Code p0442 indicates a fuel vapor leak in the EVAP control system. To fix this problem, remove and reinstall the gas cap. Clear the codes and drive to see if the codes reappear. If the code appears again replace the gas cap or inspect the system for cuts or holes in the tube or hose. good-day !

It is a leak in the return lines (fuel vapor flow) to the fuel tank could even be a defective non sealing gas cap!!!
Have it checked fumes escaping are not safe.

if you got that code from an auto parts store (for free ) they can give you a print out of trouble shoting tips you have more then the gas cap to check. gas cap is the most commen culprit.you have a rubber line to the purge tank and a rubber line from the tank to the egr valve and a rubber line from the egr valve to the throttle body they are the second most commen cause of leaks also the valve could be shot its not supposed to open durring idle if that when your light pops on could be the problem

P0442 OBD-II Trouble Code - Evaporative Emission Control System Leak Detected (small leak)

What does that mean?
This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.


Symptoms
You likely won't notice any drivability problems.


Causes
A code P0442 most likely means one or more of the following has happened:
* A loose or improperly affixed gas cap
* A non-conforming gas cap (i.e. not factory/original brand)
* A small leak/hole in a fuel vapor hose/tube
* Other small leak in EVAP system
* Faulty vent o-ring seal


Possible Solutions
With a P0442, the most common repair is to:
* Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
* Otherwise, replace the gas cap, or
* Inspect the EVAP system for cuts/holes in tubes/hoses




Fig. EVAP vent solenoid (2) on 3.1L, 3.4L, 3.5L & 3.8L, showing the connector (1) and vapor line (2)




Fig. EVAP canister purge solenoid location on 3.1L & 3.4L




Fig. EVAP purge solenoid valve (3) location on 3.5L




Hope this help, good luck.

p0455 is evap control system no purge or large leak
p0442 is evap control system leak detected (small leak)

the cause for both could actually be a loose gas cap.

Im guessing its a P0442. That means:
EVAP LEAK MONITOR MEDIUM 0.040 LEAK DETECTED
Causes of this could be a few things.
I recommend replacing the gas cap. Then take it to an auto place to get them to erase the code.
If it comes back on then...
Under the hood is a small green cap. That is the EVAP line. Follow that all the way to the gas tank and see if you see any leaks. If you do, replace/repair it.
If you dont then the only thing you honestly can do is take it to a mechanic with an EVAP Emission Leak Detector [EELD]
Good Luck!!

make sure you get a cap from the dealer. I had similar issue.... bought cap from autozone...still threw the code....thought must be something else.

ended up replacing all the vacuum lines ... still threw a code

desperate, bought new cap from dealer.... problem solved!