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P0455 code! Emission Leak Monitor Large Leak Detected

228K views 51 replies 32 participants last post by  Crusader40 
#1 ·
Hey jeepers, my 2001 Jeep wrangler 4.0L auto. Is giving codes P0455 and P0442 which my scanner says are "Evaporative Emission Leak Monitor Medium and Large Leak Detected" CAN ANYONE TELL ME WHAT THIS MEANS AND HOW IT CAN BE FIXED? THANKS! This isn't a major issue code cause I've been driving with the check engine light on for about a year!
 
#33 ·
I have the OE cap and just got P0456, any cap you'd recommend Jerry? I'll start with that, never had the code before.

This forum is the greatest!

I had code P0456 come up a few weeks ago and searched the web and was lead back to my favorite Jeep forum.
Reading this thread (and a couple of others) I decided to try a couple of things:
I purchased a locking gas cap (which I was thinking about doing anyway) but it didn't help. :facepalm:
Next, I checked out the tubing that routes near the battery and sure enough, it was worn on one side. I slapped on some RTV sealant and wrapped it with wire wrap (you know, the ribbed kind that comes in rolls) but the light didn't go out. :surrender:
I had resigned myself to the fact that I'd have to go to the dealer and pay to have it checked out (I have an extended warrenty but have a $100 deductable). :cool:
Low and behold, on day 5 after my repair, the light didn't come on and it's still off! :dance:

I love this forum, thanks for the help guys. :punk:
Can you post pics of where your leak was? I'm getting the same code and if a new cap doesn't do it I'm hunting for the leak, all help is appreciated.
 
#9 ·
Can you post a larger picture? I bought my jeep yesterday. Today: LET THE PROBLEMS BEGIN!!!

My engine light tripped and I got po455(p0455) Gross Evap Leak. In my old Volvo It was a cheap little purge valve Right on top of the engine 20 bucks and no tools needed. When I posted on the Volvo forum I got a half dozen responses immediately, all saying the exact same thing. It was a very well known failure point.

Does any body know if there's any "known issues" for jeeps with this code?
 
#16 ·
Like above I replaced some dry rotted vacuum hoses and it fixed my problem, I was getting your same code. If you look around your engine and don't find any cracked hoses you need to take it to an auto shop and have it smoke tested. The shop will connect a smoke machine to your hose system and it will reveal any leaks
 
#18 ·
Jeepatron said:
I thought i was the only one with this problem. Ive got an 01 4.0 5sp mine code is p0455 its been there every since ive got my jeep. Could this cause any major problems if its not fixed?
I was running with the code for about a year and never had any problems and went I fixed it I never really felt any difference in performance but it could have helped MPG a little
 
#21 ·
My wife's Libby throws the same code. I changed the gas cap a while back, didn't do a thing. I'm sure it is a dry-rotted hose that I haven't been able to locate yet. She's been driving it around for a while with no issues. The only issue we will have is when we go to get it inspected...it can't pass with a CEL on.
 
#26 ·
Home Made Smoke Tester?



Hi relgnarw peej ... I've got codes P0442, P0455, P0456... EVAP Leaks small/large... been there forever... gonna try to eliminate them as I want to sell it. I'm interested in how you made your "homeade smoke tester". I also have gotten gas caps, several, from Autozone. Did you ever find a good cap, and if so, where did you get it?

I have a 2003 Jeep Wrangler Freedom Edition 6 Cylinder.

Your Help will be Greatly Appreciated,

John B.
 
#24 ·
So I've been scratching my head over the p0455 code for the past month. I read pretty much every thread on WF along with other jeep forums. I did what everyone recommended - replacing the gas cap with a factory cap from an auto parts store and disconnecting the negative terminal on the battery to reset the CEL, following the fuel lines and looking for cracks, etc., but nothing worked. I didn't find any cracks so I assumed that the leak was somewhere near the gas tank. I didn't want to bite off more than I could chew by dropping the fuel tank, so I decided to suck it up and take it to a shop to get it smoked.

I just dropped it off at Firestone and they first asked me if I had replaced the gas cap (which I thought was pretty cool - I feel like the stealership would have just taken my jeep and not asked me about this before performing a diagnostic check and billing me.). I told them about everything that I've done to try to remedy the CEL code, so they performed the smoke test. Turns out that my new factory gas cap, which I purchased from a reputable auto parts store, was the culprit. :facepalm: The Firestone guys said that it wasn't the right gas cap, thus not sealing correctly, and that my fuel system did not have any other leaks. They replaced the gas cap and I'm good to go now.

So, if you get this error code in the future and try everything that is recommended by the pros here on WF, I suggest paying the extra $9 to buy a second factory gas cap just to rule it out before you pay a mechanic to do a diagnostic test. It would have saved me $128.00 today!

Dino
 
#27 ·
Hi BigDino... you said the Firestone guys replaced your gas cap... what did they replace it with? Make/Model?

Your Help will be Greatly Appreciated,

John B.
 
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