DTC Code P0456 is intermittent - Is this a serious issue? - JeepForum.com
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Unread 10-20-2008, 07:21 AM   #1
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2004 WJ 
Join Date: Oct 2008
Location: Vermont
Posts: 5
DTC Code P0456 is intermittent - Is this a serious issue?


This will be my first post here on the jeepforum and I hope that someone will be able to help me with this issue. I have a 2004 Jeep Grand Cherokee Laredo Freedom Edition that has 64,000 miles on it.

A few weeks ago while driving, my check engine light came on. (I had just put gas in the vehicle the night before). I took it to the local auto parts store and they plugged in the OBD II sensor and it gave the code P0456 (EVAP Monitor Leak Detected - Very Small)

My dad said that it could have been just bad gas or something so I waited a few days... it did go away... but then came back again, and is still on now.

Could this have anything to do with the 10% ethanol mix in gas now? I mean... cars arent designed to run with that in there really are they?

I went online and searched the code for my jeep and I found a TSB bulletin for "fake p0456 codes" on the 2002 and 2003 models of Jeep Grand Cherokee...

Has anyone else had this code? Is it possible to fix it without bringing it to the dealership?

thanks in advance!

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Unread 11-27-2008, 09:15 PM   #2
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2003 TJ Wrangler 
Join Date: Oct 2008
Location: louisiana
Posts: 9

Hey man I've been having the same problem with my 03 tj and have talked to a few people and most say its the gas cap. I've cleared the code twice now and find it hard to believe that this is the problem but can't offer a better explaination. I'll keep you posted in case I get a better fix.
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Unread 11-27-2008, 10:35 PM   #3
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1997 ZJ 
Join Date: Jun 2008
Location: Las Vegas
Posts: 2,921
Well it often is this gas cap failing to seal. Usually the gasket cracks. Or the rubber sections between the meetal evac lines are heat rotting. The easiest fix is to buy a new gas cap. I've heard even from the stealership it's like $15. I would start there. If that isn't it I would inspect as much of the evac system for cracks or leaks as possible. If you are still having a problem take it to a shop you trust and have them perform a smoke test. I paid $127 for the test on my 01 xj last month. They fixed the leak for free just using some rubber hose. Good luck a real stubborn problem that is pretty common. I couldn't pass an emissions test because of this error code thanks to the greenie commies in washington and cali.
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Unread 01-22-2012, 10:31 AM   #4
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2004 FSJ Cherokee 
Join Date: Apr 2010
Location: Louisville, Ky
Posts: 7
I have an 04 GC Special Edition and got this code about 2 weeks ago, had it read and reset, then it came back about a week later. From my local autozone, the readout "probable causes" are (1) fuel cap, (2) Evap cannister broke or hose leak, (3) purge solednoid defective, (4) vacuum leak at engine.

I'm approaching this methodically. First I'm going to discount the fuel cap by wrapping saran wrap around the cap before screwing it in to eliminate the cap as a possibility. I'm in the process of checking this now. Next I'll check for leaks, not sure how to easily do this, any suggestions??
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Unread 04-14-2012, 09:39 AM   #5
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1996 ZJ 
Join Date: Jan 2012
Location: hopewell, va
Posts: 2,049
If the az guy cleared the code for you,next time you see him tell him its against federal law to clear codes,now ill admit most folks dont care about it,its still against the law
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