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Discussion Starter #1 (Edited)
Its only been a few weeks since buying the Commander and have already addressed a parasitic draw issue caused by the sunroof.... Thread here. https://www.jeepcommander.com/forums/10-electronics-nav-discussion/74699-parasitic-draw-found-fixed.html

Unfortunately, over the past week a P0452 code keeps coming back after being cleared. "P0452: Emission Control System Pressure Sensor Low Input"

So.... is the sensor usually the culprit, or would the "low input" indicate there is an abnormally low pressure (leak) in the system?

In addition, looking for the EVAP pressure sensor online, Im unsure as to where exactly the sensor is or what it looks like. Am I correct in the assumption that it is part of the "FUEL VAPOR CANISTER LEAK DETECTION PUMP" or as RockOuto calls is a "Vapor Canister Purge Valve / Solenoid"? This fits to the charcoal filter canister and upon removal, it appears the wiring harness connecting to it actually only powers what looks to me like a pressure sensor within the unit. The "check valve" within the unit seems to be mechanical contraption. The image after the link shows the two shiny circle parts which I believe are the pressure sensors itself. Is this the Pressure sensor?

The part in question... https://www.rockauto.com/en/moreinfo.php?pk=3447567&cc=1434535&jsn=1095&_nck=Ekt6BqBF1pwlXdx0gYlm1esw98pF26vehMm/GG3C/l2QOXSJubi7WSpUmUSdg3OxWOs2f5z9h422EONy36O0PjCuaadDqI1r86y/vJ1lBqy8eOR0sg7BszHWEnTZqwKCjV54dylwVqaI/RBihvVB2df3QwNeh1KoCe8u0CRrfLbbcwuW2fC8d/BfzfbdOhJ2DbxoQRV4QJRaTaEm0EntWNmRPCjitQv6W6BRqtV/AeYapcruYPMHqHKRoj7eKNabfGZfGm5fNTF/lp3Fxm1L79quFC8K9BLW0WCSiWZGXWfOV66RAolImytymSVswef***OOTfaZWpcT09fHPvBPns3CSgQlEAJZxw2BYQ2cp0p3BanMIls3/dlGj+2/MoWxGokNYMoLyoXR6O3l9rOTrntuSejSD+1d






Furthermore, is it wishfull thinking that the fuel cap may be whats causing a low pressure reading "if" the sensor is actually ok?

I dunno.... guess Ill throw one of the above units AND a fuel cap at it and see what happens. :surprise:

The vehicle is also very hard to put gas in as it keeps tripping the pump nozzle thinking is full when its not.... I took off all the lines having to do with the fill tube assembly and the evap canister etc and blew compressed air through them and found NO obstruction.
 

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Don't know if this helps or not, but I found a slightly different result;

Jeep Grand Cherokee WJ - Diagnostic Trouble Codes

P0452: Evaporative Emission Control System Pressure Sensor Low Input; NVLD pressure switch stuck closed.

As far the part you in the pic you posted, I couldn't tell you.
 

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Found this as well; NVLD stands for Natural Vapor Leak Detection Pump.

https://www.engine-codes.com/p0452_jeep.html

P0452 Jeep Meaning:

The Evaporative Emission System (EVAP) control system pressure sensor detects pressure in the purge line. The sensor output voltage to the Engine Control Module (ECM) increases as pressure increases. The EVAP control system pressure sensor is not used to control the engine system. It is used only for on board diagnosis.

 

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Discussion Starter #4 (Edited)

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I have EVAP problems as well. The shop smoke tested the EVAP system and found a leak at the leak detection pump - it's stuck open. I haven't ordered one yet but just thought I'd let you know mine has failed as well.
 

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Discussion Starter #8
I have EVAP problems as well. The shop smoke tested the EVAP system and found a leak at the leak detection pump - it's stuck open. I haven't ordered one yet but just thought I'd let you know mine has failed as well.
What code did you have?
 

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P0440 is persistent.

P0456 and P0457 were up for a few months and recently didn't come back.

Sent from my SM-G955U using Tapatalk
 

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Discussion Starter #10
P0440 is persistent.

P0456 and P0457 were up for a few months and recently didn't come back.

Sent from my SM-G955U using Tapatalk
Sounds like you have a leak in the evap system somewhere based on those codes.... you replace the gas cap and clear the code? You can clear the code without an OBD scanner by disconnecting both battery terminals and touching them together for about 15 seconds.
 

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I'm confused... I already said the leak is at the leak detection pump from a smoke test in the post you quoted.

I do have a code reader.
 

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LooseCannon - Did you fix your issue?

I figured out Jeep calls that first item you pictured the "ESIM" while Rock Auto calls it the "Leak detection pump."
Before I had mine smoke tested, I also had a crack in the charcoal canister that I fixed with epoxy. Thanks to the results of the smoke test, I bought a new ESIM or whatever you want to call it, and the replacement fit much tighter.
Code hasn't been back yet, so I hope I fixed my issue.

I would not, however, throw the parts cannon at this issue without doing some diag yourself and possibly doing/having a shop do a smoke test.
Also make sure you have vacuum at the side of the purge valve going back to the tank.

EDIT: Just as an FYI, the "ESIM" seems to have two settings: vent to atmospheric or sealed. Mine seems to have failed open, producing the large evap leak and "check gas cap" message.
 

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Sounds like you have a leak in the evap system somewhere based on those codes.... you replace the gas cap and clear the code? You can clear the code without an OBD scanner by disconnecting both battery terminals and touching them together for about 15 seconds.
I can see taking both battery terminals off - but I don't think holding the 2 terminals together for 15 seconds is a very good idea at all.

I wouldn't recommend that solution to anybody @LooseCannon, even though it may have worked for you; It's probably best to buy an OBD-II scanner of some sort and clear the codes properly. In this day & age, there are quite few OBD-II scanners on the market that are cheap enough.
 

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Blue, while I will echo your comment I don't specifically recommend it, this is actually a common technique with electronics to quickly discharge the capacitors before opening things like CRT monitors or power supplies. But again, I cannot promise it won't harm vehicle electronics.

To add a little bit of safety to this method, you could disconnect the positive terminal, then turn all you interior lights on. It would still be a path to ground, but there's some resistance. Click them back off after a minute, connect the battery, and Bob's your uncle.
 

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Excellent, thank you, those posts are right on point. I will also search the forum myself — I didn’t mean to make you look for me.

I just found the Tapatalk app today and am using for this forum — very convenient!


Sent from my iPhone using Tapatalk
 

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Excellent, thank you, those posts are right on point. I will also search the forum myself — I didn’t mean to make you look for me.

I just found the Tapatalk app today and am using for this forum — very convenient!


Sent from my iPhone using Tapatalk
CJC; you're new here, so it's understandable.

I don't mind doing some of the leg work to get folks pointed in the right direction.
 

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Excellent, thank you, those posts are right on point. I will also search the forum myself — I didn’t mean to make you look for me.

I just found the Tapatalk app today and am using for this forum — very convenient!


Sent from my iPhone using Tapatalk


I use tatatalk also. I like it for the most part, but I can’t see the left side bar details to know details on what Jeep people have. I probably need to change some settings.


Sent from my iPad using Tapatalk
 

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I have EVAP problems as well. The shop smoke tested the EVAP system and found a leak at the leak detection pump - it's stuck open. I haven't ordered one yet but just thought I'd let you know mine has failed as well.
STUCK OPEN... again. 2005 Jeep Grand Cherokee,only 60,000 single owner. I have had to spend $2000 at jeep dealer over the past year for this issue. It is ridiculous. Must be an inherent problem with Jeeps. The computer diagnostic supposedly just indicates "small evap leak" with no pin point as to where... okay. 2/20/20 - picking up today. Part under warranty. "PCM valve recognizing, but nlvd not." So it took 5 days to fine out this same part is replaced for the third time in 2 years. They wont give me old part because it has to go back to Jeep for warranty money back to dealer. Too bad I love Jeeps. Now I read that newer Jeep owners are having the same issue... hummm.
 

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I have been chasing the same issue with my Jeep Commander over the last three years, getting the P0456 code. I have paid for three smoke tests and replaced just about every part of the EVAP system, including the vapor canister purge solenoid (twice) to the carbon canister and pump and also the fuel neck hose, which the smoke test showed had a small leak (i paid to have that done, as it required dropping the fuel tank). Each time the code would appear within a week or so.

The last thing that I did was strap the vapor canister purge solenoid firmly down when I noticed that its plastic mount had broken and so it could move (the movement perhaps was causing the tubes going into it to slide down?). Not sure if that was the issue, but that was two months ago, and I haven't gotten the code since.

The good news is that the problem doesn't seem to affect drive-ability at all. But the vehicle won't pass my state's emission testing if the code is showing (I envy those of you who live in states without emission testing).

I have another newer Jeep and also two Dodges and do not have this issue with any of them.
 
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