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post #1 of 15 Old 09-21-2017, 01:30 PM Thread Starter
ComfortablyNumb
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Location of Leak Detection Pump

2014 Grand Cherokee Ltd.; check engine light on; code is P0456; specific part indicated = Fuel Vapor Leak Detection Pump

Can someone please tell me where this part is located on my vehicle? I can't even find a schematic of it in relation to the entire vehicle. Many thanks.

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post #2 of 15 Old 09-21-2017, 01:36 PM
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Originally Posted by ComfortablyNumb View Post
2014 Grand Cherokee Ltd.; check engine light on; code is P0456; specific part indicated = Fuel Vapor Leak Detection Pump

Can someone please tell me where this part is located on my vehicle? I can't even find a schematic of it in relation to the entire vehicle. Many thanks.
First step is to tighten your gas cap. In the past when I have gotten that code my issue where with the gas cap. But there could be other issues.

Search around here and you will find a list of things to check.

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post #3 of 15 Old 09-21-2017, 03:17 PM
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First step is to tighten your gas cap. In the past when I have gotten that code my issue where with the gas cap. But there could be other issues.

Search around here and you will find a list of things to check.
I don't have an answer for the OP other than the '14 JGC doesn't have a gas cap.

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post #4 of 15 Old 09-21-2017, 04:00 PM Thread Starter
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Yes, I don't have a gas cap. That was the first thing I thought about since I've had it happen on other vehicles. I'm not sure what I have other than a pop open door. I guess there could be a leak in that apparatus but with Jeep's prices, that will be last on my list.

For $16.99, I can put a Fuel Vapor Leak Detection Pump on the vehicle. That's what the read-out indicated at Auto Zone. Not only did it say P0456, but it specified the exact part needed and this was it (EMS1003).

My problem is I don't know where it is. The closest I've come to finding it is in a YOU TUBE silent video that lasts about 20 seconds. It looks like the guy has popped the rivets holding the dust cover at the left rear quarter panel wheel well just next to the gas tank. It's an easy fix once you get in. He wasn't working on a 2014 however so I had hoped to get a better idea before diving in.
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post #5 of 15 Old 09-21-2017, 04:46 PM
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Dunno, according to my FSM and my ODB reader data base, P0456 is a small leak in the EVAP Purge System. This code gets set when the monitor test is run, which will only run if the small EVAP test passes..

This specific error code could be caused by a leak in the purge system, bad purge solenoid, or bad integrity monitor switch (sometimes called a pump in some parts books but its really just a monitor). A gas cap/door leak can also cause this as just about any leak in the system, but you will likely have other errors. Dunno where the motor term comes from, just reading the book and it seems its the same location regardless of what its called..

You may want to check if there is a TSB on the subject for your model year. Many times a ECU flash corrects problems like this.

The pump/switch itself is located on the vapor canister which is buried under the left rear tire splash shield. You need to take the tire and splash shield off to get to it. #1 in the diagram below. $20 from a discount OEM parts outlet.
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post #6 of 15 Old 09-21-2017, 07:50 PM Thread Starter
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Thank you ColdCase. You have definitely identified the part that was called for by the Auto Zone analysis. Also, the location that you mention is the same as in the You Tube video I mentioned. I went back and found the video again. The guy is replacing this "pump" on a 2012 Grand Cherokee and he didn't have to take off the tire. Have a look:
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post #7 of 15 Old 09-22-2017, 01:28 PM Thread Starter
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Update. Just returned from having this problem corrected (fingers crossed). I went to Auto Zone early this morning to pick up the only fuel vapor leak detection pump in Columbia, SC. They re-ran the test and advised me not to purchase the part until I have a leak test done. The report indicated a "very small leak."

I went to Firestone and had the test done. They said I have 0 leaks. Their scan said to have the dealer do a flash and if that doesn't correct the issue then install a fuel vapor leak detection pump. Of course the dealer is probably going to want to do the diagnosis all over again and charge me for the flash.

I told the tech to hang on a few minutes while I caught a ride back to Auto Zone where I purchased the pump. The tech installed it and the check engine light went off by itself. Hopefully this solved the problem and I avoided another expensive trip to the dealer. [Two weeks ago I had to go to the dealer because my 2014 (66,000 miles) was skipping badly. $300 got me a diagnosis, a new #4 coil, and a spark plug. Turn around time was 3 days.]

For any of you who encounter a similar problem, ColdCase nailed the location for the "pump." It's next to the canister in the left rear wheel well. The tech remove the left rear tire and took out 4 or 5 pop snaps and one screw. This allowed the dust flap to partially drop, and the "pump" was easily accessed.

This has been one of the most pleasant car experience days I've ever had. I encountered true professionals every step of the way. Very honest people who were not trying to gouge me. I'll definitely be trading at these business in the future.
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post #8 of 15 Old 09-22-2017, 02:01 PM
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Thanks for the update, let us know how it goes.

Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #9 of 15 Old 10-03-2017, 11:31 AM
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I also have a '14 GC (Overland Hemi) and I too get this code about every 3 to 4 fill ups. I believe the problem resides within the capless fuel filler system; I think it just fails to close tightly every time. I usually use the fuel funnel in the trunk to try and reset the valve and then I use my personal code reader to clear the code. I'm usually good to go for another 3-4 tanks of gas before it does it again.


Has anyone else noticed this? Is there an easy way to convert the capless system to one with a manual cap so I don't have to keep dealing with this?


Thanks.
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post #10 of 15 Old 10-03-2017, 01:50 PM
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This may be one of those faults that is set after 3 failures. So it may be failing after each fill, its just not setting the check light till the third failure. You should be able to use your code reader to check pending faults.

Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #11 of 15 Old 10-03-2017, 02:43 PM
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Quote:
Originally Posted by ColdCase View Post
This may be one of those faults that is set after 3 failures. So it may be failing after each fill, its just not setting the check light till the third failure. You should be able to use your code reader to check pending faults.

That's a really important piece of advise. I'll have to check that out.


Last fall I received a similar error code (P0455 or P0456 for a small leak) for which the dealer investigated and found a leak somewhere and replaced a part (I have the paperwork but I can't remember off hand). Since then the code indicates a large leak that I've been told is more consistent with a loose gas cap than a small leak somewhere in the system; but I'm no expert.
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post #12 of 15 Old 10-03-2017, 02:48 PM
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Quote:
Originally Posted by ColdCase View Post
This may be one of those faults that is set after 3 failures. So it may be failing after each fill, its just not setting the check light till the third failure. You should be able to use your code reader to check pending faults.
Just another thought; I remember reading the Fuel Evap System only runs a check when the fuel level is between ~75% and ~25% full. Also, if this code does only trip after three readings, shouldn't it occur once I'm below 75% full and have made three trips in the car? Why would it be specific to when I refuel? With my original problem last fall I was able to reset the code, but it recurred within a few days, which is what prompted me to have it investigated.


Thanks for the help.
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post #13 of 15 Old 10-03-2017, 06:54 PM
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My understanding is that the Evap monitor purge test has a couple stages.

The small leak code is P0456

The large leak code is P0455

The system test code is P0440

Operation, as you see there are a wide variety of inputs, like temperature, key off cycles, fuel level that can cause codes to be set at what seems to be strange intervals.... :

During refueling, pressure is built up in the evaporative system. When pressure reaches approximately .5 inches of water, the large check valve in the ESIM unseats and pressure vents to the fresh air filter.

Conversely, when the system cools, and the resulting vacuum lifts the small check valve from its seat and allows fresh air to enter the system through the fresh air inlet and relieves the vacuum condition. When a calibrated amount of vacuum is achieved in the evaporative system, the diaphragm is pulled inward, pushing on the spring and closing the contacts.

Thesystem conducts test on the evaporative system as follows: An engine off, non-intrusive test for small leaks and an engine running, intrusive test for medium/large leaks.

The ESIM weights seal the evaporative system during engine off conditions. If the evaporative system is sealed, it will be pulled into a vacuum, either due to the cool down from operating temperature or diurnal ambient temperature cycling. When the vacuum in the system exceeds about 1” H20, the vacuum switch closes. The switch closure sends a signal to the PCM. In order to pass the non-intrusive small leak test, the ESIM switch must close within a calculated amount of time and within a specified amount of key-off events.

If the ESIM switch does not close as specified, the test is considered inconclusive and the intrusive engine running test will be run during the next key-on cycle. This intrusive test will run on the next cold engine running condition.

Conditions for running the intrusive test are:

•After the vehicle is started, the engine coolant temperature must be within 50 F (10 C) of ambient to indicate a cold start.
•The fuel level must be between 12% and 88%.
•The engine must be in closed loop.
•Manifold vacuum must be greater than a minimum specified value.
•Ambient temperature must be between 39 F and 98 F (4 C and 37 C) and the elevation level must be below 8500 feet (2591 meters).

The test is accomplished by the PCM activating the purge solenoid to create a vacuum in the evaporative system. The PCM then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the switch does not close, then a general evaporative failure is recorded. The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Even when all of the thresholds are met, a small leak won’t be recorded until after the medium/large leak monitor has been run. This is accomplished by the PCM activating the purge solenoid to create a vacuum in the evaporative system. The PCM then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the medium/large leak test runs and the ESIM switch doesn’t close, a general evaporative test is run. The purge solenoid is activated for approximately 10 seconds, increasing the amount of vacuum in the system. If the ESIM switch closes after the extended purge activation, a large leak fault is generated. If the switch doesn’t close, a general evaporative system fault is generated.

The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Stage one of the purge monitor is non-intrusive. The PCM monitors the purge vapor ratio. If the ratio is above a calibrated specification, the monitor passes. Stage two is an intrusive test and it runs only if stage one fails. During the stage two test, the PCM commands the purge solenoid to flow at a specified rate to force the purge vapor ratio to update. The vapor ratio is compared to a calibrated specification and if it is less than specified, a one-trip failure is recorded.

The ESIM switch stuck closed monitor checks to see if the switch is stuck closed. This is a power down test that runs at key-off; when the PCM sees 0 RPM’s, the purge solenoid is energized for a maximum of 30 seconds, venting any vacuum trapped in the evaporative system. If the switch opens or was open before the test began, the monitor passes. If the switch doesn’t open, the monitor fails. This is a two-trip MIL. The star scan tool can be used to force the ESIM switch stick closed monitor to run.

The PCM also uses the ESIM to detect a loose or missing gas cap. The PCM controller looks for a change in the fuel level (25% minimum) and then gas cap is loose or missing. If a medium/large leak is detected, a loose gas cap light illuminates and a pending one-trip fault code is set. On the PCM, this is a three-trip fault before the code matures.

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post #14 of 15 Old 10-04-2017, 09:28 AM Thread Starter
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I have an update that may or may not mean anything, but since I started all of this: I thought Firestone had corrected my problem by confirming "no leaks" and, at my request, installing a new EVAP leak detection pump. The check engine light went off on its own and I was good to go--or so I thought.

After a few days, the light came back on again. I disconnected the battery and it went off for a couple of days. Then it returned. I went back to AutoZone and got a similar reading as before. I said f_ _k it, I'm going to the dealer.

I got lucky and found a service mgr. I know who loves to please. He took his computer out to my car and did some diagnostics. Even though Firestone's printout had said there is a flash for 2014, the serv. mgr. said there's not one indicated for my car. He did a couple of things and the check engine light went off. This was three days ago and it's still off. He didn't charge me.

I'm beginning to think he probably did something similar to what B05T0N22 mentions with his personal code reader. I guess we'll find out soon.
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post #15 of 15 Old 10-04-2017, 09:55 AM
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The Small leak flash for 2014 was for a certain build date range, so it may not apply to you.. There have been PCM system performance flashes that may address this, some 2014s came off the production line with a small split in the evap hose. But yours may also be outside its date range.

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Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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