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Discussion Starter · #1 ·
I have a P0456 that will come on only after my 2009 2.4l Patriot after it has sat out overnight or a few days when there is heavy rain (1 or more inches of rain). High humidity or light rain does not seem to set the code.

It does not come on if I am driving in the heavy rain.

I did most of the normal items:
-Replace gas cap with factory one (made sure it was tight)
-sanded down filler neck to make sure there are no rusty bumps
-tightened filler neck hose clamps
-visually checked the lines in the engine compartment and at the evaporator canister in the rear. Everything looked okay but did not do a smoke check.
-checked electrical connections

Since this only happens when it is pretty moist out, I was wondering if others ran into this issue. I hate to start plugging more parts in.
 

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Discussion Starter · #2 ·
With springtime rains and moisture, I thought I would give my P0456 Code (Small Evp Leak) issue another try.

In addition to the above, I also replaced the Fuel Vapor Leak Detection Pump. Unfortunately, it did not fix the problem. With nearly 80% humidity, once I started the engine, the CEL came on with the same code.

I can drive for weeks in dry weather without any issues...more than 70% or so humidity, CEL comes on.
 

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With springtime rains and moisture, I thought I would give my P0456 Code (Small Evp Leak) issue another try.

In addition to the above, I also replaced the Fuel Vapor Leak Detection Pump. Unfortunately, it did not fix the problem. With nearly 80% humidity, once I started the engine, the CEL came on with the same code.

I can drive for weeks in dry weather without any issues...more than 70% or so humidity, CEL comes on.
Now i have witnessed the CEL going off on its own after the car cylces a bit but others kept mentioning disconnecting the negative battery terminal for 10 minutes to clear it. I did that and it did clear it. Drive multiple times to see if it comes back on.

Id say go after the purge valve next if it doesnt help. If that doesnt, which is what im determining for myself, go for a new charcoal canister. Though my cars CEL is P0441. I had the P0456 code last year when all i did was replace the gas cap and clean.
 

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Discussion Starter · #4 · (Edited)
I went ahead and replaced the Vapor Canister Purge Valve...I opted for the one with the vacuum hoses for a couple of extra dollars.

With rain coming...will give it another try.

What I replaced over time and as of today (in addition to checking hoses and clamps):
-Factory gas cap (and filed down filler)
-Fuel Vapor Leak Detection Pump
-Vapor Canister Purge Valve
 

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Discussion Starter · #7 ·
How much did you you file on the the filler.
I took a short file and made sure any rust was off and that there would be a good seal all the way around. I also lubed the gas cap seal. I made sure the clamps on the filler hose were tight too.

So far, after two heavy rains, no code but will not jinx it yet!
 

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After a few weeks of replacing the purge valve and vapor leak detector pump in the rear i have had no CEL come up. I managed to get it to pass Rhode Island inspection also.
 

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That P0456 trouble code is by far the most common one I have, all the time, going back to when the car was 5 yrs old and continuing constantly to this day. I have cleaned the gasket on the gas cap, lubricated the gasket on the gas cap, and replaced the gasket on the gas cap. Also took a brass wire wheel and a Dremel tool and carefully chased all the rust and pits around the edge of the metal filler neck where the gas cap seals (stuff a rag into the opening of the filler neck to prevent rusty debris from going into the gas tank, then use a shop vac to suck all that out before pulling out the rag). After cleaning up the neck down to good clean bare metal, I then coated it with a thinned mixture of 5-minute epoxy to prevent almost instant re-rusting of the exposed steel. And also replaced the gas cap entirely, which works for a while.

The P0456 trouble code continues to this day, and never escalates to a larger vacuum leak, but I cannot seem to make it go away permanently for any length of time. Always seems to resurface just before the the yearly state inspection comes around, and then I have to figure out some magic way to get it to disappear before it gets inspected. Sigh...
 

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Discussion Starter · #11 ·
My P0456 trouble code has come back with the hot, humid weather. It seems to come on when humid no matter the temperature.

I placed more lube on the new gas cap seal without luck (cleaned area, etc.).

With the garage at over 100 degrees, I noticed a slight raw gas smell near the gas cap and no signs of leaks.

The only items I have not replaced is the vapor canister (expensive) and the gas tank seal where I see that can pop the code at times.
 

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I have no experience with this problem and am just sharing a bit of information from the factory service manual. The three main areas it identifies as possible causes are:

Evap Purge solenoid vacuum supply - Evap purge hose/Tube obstruction - Evap system leak

Beyond the recommendation to check ALL hose and joint possibilities for leaks, they then go into a detailed diagnostic routine with special equipment to track down the leak.

The leak information shows three "zones" that have to be checked with 31 possible leak areas - the gas cap being one.

Google "jeep ESIM" for information on that sensor/valve too.

Sorry that I have no more practical suggestions to help you.
 

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Discussion Starter · #13 ·
Thanks.

I noticed the last two times this happened on hot days (90+ or 100 Degree garage) that I had filled up (stopped when it first clicked off) and then drove a couple of miles and parked it.
 

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Discussion Starter · #14 · (Edited)
I believe I finally fixed the P0456 code with the help of this post: smell of gas after filling tank

I had a rusty locking ring and it had cracked the top of the fuel pump. I ended up repairing the crack with a fuel and ethanol resistant epoxy and wired brushed and repainted the locking ring.

So far, no fuel smell or leak or CEL. If the crack comes back I will just have to replace the pump.
92320
 

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I believe I finally fixed the P0456 code with the help of this post: smell of gas after filling tank

I had a rusty locking ring and it had cracked the top of the fuel pump. I ended up repairing the crack with a fuel and ethanol resistant epoxy and wired brushed and repainted the locking ring.

So far, no fuel smell or leak or CEL. If the crack comes back I will just have to replace the pump.
View attachment 92320
 

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Living in Phoenix , Arizona. Summer at 115 degrees Fahrenheit sand storms, rain storms. Etc got very humid and my check engine came up come P0456. The title caught my attention because of the weather situation I have done everything from gas cap to fuel vapor leak detection. How do I access my fuel pump to check for a cracked locking ring ? Thank you. I need to pass emissions 😞
 

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2017 Jeep Patriot 75th Anniversary Edition
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I get the same code when the temperature does a big swing. The code is also permanently set in the ECU so you would need either Appcar, or a DRBIII to clear those codes (those OTC readers will not clear permanent codes, and I don't think a battery pull will do it either). IIRC stuff like that and the EDR along with the vehicles firmware the data is saved on NVRAM so with a loss of power the data is preserved.
 

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Discussion Starter · #18 ·
Living in Phoenix , Arizona. Summer at 115 degrees Fahrenheit sand storms, rain storms. Etc got very humid and my check engine came up come P0456. The title caught my attention because of the weather situation I have done everything from gas cap to fuel vapor leak detection. How do I access my fuel pump to check for a cracked locking ring ? Thank you. I need to pass emissions 😞
The fuel tank is under the rear seat...it is pretty easy to get to.
 
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