Code P0456 = Evaporative Emissions System - Small leak detected - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 30 (permalink) Old 01-02-2009, 09:57 PM Thread Starter
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Code P0456 = Evaporative Emissions System - Small leak detected

My CEL (check engine light) came on this past Monday and I checked for codes with the three key turns method and got P0456. When I looked it up it said:

Evaporative Emissions System - Small leak detected

What does that mean?
The Powertrain Control Module (PCM) at different times performs various tests on the EVAP system. OBD II Enhanced EVAP systems are in place to keep fuel tank vapors from venting into the atmosphere, and instead purges them into the engine to be burned. Regular pressure tests are conducted by the PCM to monitor the sealed system for leaks. The PCM monitors the EVAP system pressure by watching the Fuel tank pressure sensor (FTP). When the sensor indicates a small leak in the EVAP system, this code is set.

Potential Symptoms
There will likely be no noticeable symptoms other than the Malfunction Indicator Lamp (MIL). This is because the EVAP system is a closed system and only controls fuel tank vapors, not engine management.

Causes

Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause:
  • A small leak in any of the EVAP hoses or fuel tank hoses
  • A small leak in the purge valve or vent valve
  • The EVAP Canister may be leaking
So I checked the gas cap and still got the code and the CEL has been on all week. I filled up my tank today and the CEL went out. ????????

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Last edited by jeep5253; 03-07-2009 at 07:06 PM.
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post #2 of 30 (permalink) Old 01-02-2009, 10:14 PM
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Full tank = No or low vapors. If it's not the cap it will probably come back on.

How did you check the cap? I've seen the cap seal get twisted before and adjusting has cleared the problem.
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post #3 of 30 (permalink) Old 01-02-2009, 10:16 PM Thread Starter
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Quote:
Originally Posted by TYMAC View Post
Full tank = No or low vapors. If it's not the cap it will probably come back on.

How did you check the cap? I've seen the cap seal get twisted before and adjusting has cleared the problem.
I took it off and put it back on several times. It seemed to be fitting ok.

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post #4 of 30 (permalink) Old 01-03-2009, 01:09 PM
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I had this issue many times. 1st time at the shop they inspected and tighten hoses. The second time the gas cap was replaced (i was very doubtful). It's been quite a while since I've had another 0456 (had one since the cap was replaced). Overall the repair was effective IMO despite the single occurrence.
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post #5 of 30 (permalink) Old 02-01-2010, 01:11 AM
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Check engine light repeatedly comes on.....

...then goes off after a few days. No noticeable change in performance, MPG, etc. - only that dreaded light is on. I have noticed it is usually a few days after I fill up. It will come on when I get to around 2/3 to 1/2 tank, stay around for a few days, then one morning its gone until the next fill up. I've done the three key turns and get "P 0456" on the display, which I think is a misfire, reading IIRC. Have never received a notice that the gas cap is loose. Any ideas????
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post #6 of 30 (permalink) Old 02-01-2010, 01:29 AM Thread Starter
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https://www.jeepcommander.com/forums/showthread.php?t=7381&highlight=P0456


.

2006 Steel Blue 5.7L HEMI Limited 4x4 Build Date: June 9, 2006 Hour 14
Interior: Dark Slate/Light Graystone with Saddle Brown Leather Seats
Quadra-Drive II, NAV, DVD, Trailer Tow Group IV, Off-Road Group II, Remote Start, UConnect, Rear Backup Camera, Chrome Wheels,
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post #7 of 30 (permalink) Old 02-01-2010, 04:47 AM
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Moved your question to the linked thread.



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post #8 of 30 (permalink) Old 02-01-2010, 05:40 AM
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I had the same problem with 2006 scion Tc. Check engine light came on flagging my EVAP system. Everytime I checked the gas cap it seemed tight. I chose to replace the gas cap because it was cheap. Once the cap was replaced, I cleared the code by disconnecting the neg. battery terminal for about 2 mins, and it has been going good ever since then, about 5000 miles now.
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post #9 of 30 (permalink) Old 02-01-2010, 04:58 PM
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Doesn't the Jeep have a message that says "tighten gas cap" in the display?
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post #10 of 30 (permalink) Old 03-11-2010, 03:30 PM
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I just got the same code on my '08 Commander. P0456 Checked the gas cap (looks good) and filled the tank. light is still on.
I'm gonna try to get it to the dealer next week, but just want to make sure I'm understanding the warranty correctly.
Pretty much anything in the EVAP system should be covered under warranty right? The truck has 18K miles and was purchased new 13 months ago.
Thanks
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