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My wife has a 2004 Pathfinder and she got a p0455 code (evap gross leak, large evap leak). Took to the dealer, they changed charcoal canister, vent valve, purge valve. Then p0455 code went away, then we got p1456 code (small evap leak). Dealer then changed gas cap, still got p1456 code. Took back to dealer after 1 month, they charged $185 diagnostic fee, said it was stuck vent valve. I researched, bought new fuel tank pressure sensor and vent valve. I installed both, still got p1456 code. On my work day off, I got under car, removed canister (I tested it, good). I noticed rubber hose coming from gas tank to canister was stretchy, so I bought new fuel hose. I cut back a little bit of the purge line rubber hose (it was stretchy). Also I bought new clamps (ones where you use screwdriver to tighten). Installed the new fuel hose (that connects to the canister), 3 new clamps for the 3 hoses that attach to the canister (vent, purge and fuel). Bingo!!! No more codes pop up (no more CEL check engine light). No more evap leaks. Hope this helps somebody.

Before you replace the valve or other components check your lines! lines are known to crack and dry rot and it will be a lot cheaper to fix.

This is the best and clearest explanation I have seen of this. Thank you!

Great info. Calm clear description. I'm 75 year old woman trying figure out problem with my car. Mechanics charge so much so want to informed before take my car in. Wish I could still do simple maintenance one my car.

Love your videos. You explain them in every day terms and do not make us feel inferior because of our lack of knowledge. Keep up the great work.

Awesome video, I was in the Automotive field for 25 years, mostly sales, but your videos always are easy to understand and always right on the money for the diagnostics he talks about.

One more tip on the gas cap, make sure it is clean and free of debris. If it's a bit dirty, just get some alcohol wipes and clean both the inside of the cap and the rim of the filler neck. That is one of the most common problems I've seen with the P0440 code

Just a note, You guys at 1A auto are definitely, #1A. I disassembled my 350 to remove my heads and assembled it just but watching your video. Just recently I watched the video for Evan code and again. Simple and thorough. Thanks guys Dino Edmonton, Ab. Canada

Last week, I got a PO446 code on my 2011 GMC Terrain 3.0L, Took it to my repair shop. They used smoke to identify an evap leak coming from my gas cap, so I ended up paying them $62 for a new gas cap, $220 overall for the repair (labor, part, and Credit Card processing fee!. After one week, the code reappeared, so I'm going back to the shop to see if the leak is coming from the gas cap area or other places. Thanks for the video. Well done.

This video explains a lot. I had 2 different shops that did smoke test, and neither could find it. The last shop suggested going to the dealer. I have a 2010 Jeep Grand Cherokee, and experience with what may be causing this small leak on this type of vehicle. Code is a po456. Some type of pump was replaced, which in this video I didn’t see or hear about a pump. It was done before the smoke test. I think the pump and labor was under 100, and they told me it may or may not be the problem. 2 smoke test later , I still have a problem.

this was the most soothing and informative video.... came here to learn about the EVAP system, subscribed for the guy’s voice and great presentation. so chill! thank you!

As an old, retired electrical engineer I am very impressed with your teaching skills. Repairing my cars is one of my hobbies, but sometimes I am getting stuck into hidden specific manufacturing problems, like a fuse found under the wax paper insolation on a small AC transformer. Anyhow, I would greatly appreciate if you could help me troubleshoot my 2003 BMW 745Li, which started with not accepting more than 1/2 tank fuel (except when dispensing very, very little at the time), and lately getting the so popular check engine light on with the P0444 code on it. I disconnected and tested the purge valve and seems to be perfectly fine, opening and closing promptly when applying 12v to it. It may be that the purge valve intake hose having a small leak at the connection to the other hose going to the charcoal canister is triggering the P0444 code, but I do not believe this has anything to do with the tank not accepting more than half fuel. BTW, there is no pressure, nor vacuum at the filling cap after driving the car. Could you please feed back with your expertise/experience on this? Thanks a million, Chris

I love 1a auto, these are the exact the videos I look for when in need of help fixing my own vehicle

1A You are gentlemen and Scholars.

Thank you for this simple and easy and right to the point video 👍

Extremely helpful. Now I know where to begin in solving my problem. Without this understanding it was hard to know where to begin.

I found it easier to take the bolt out and then remove the connections. Good video, helped me out.

Thanks for the Video. It helps to easily understand the EVAP system.

Diesel very good tips for checking the evap system on a car, however… I ran into the trouble of replacing the filler neck on my 04 trailblazer… using a Dorman part… come to find out these Filler necks do not seal to the GM gas cap.. took me a whole year to figure out what was wrong…. I could not find anyone who could check my gas cap for me…… I purchased another neck thinking I had a defective one as well as two caps…. When I attempted to apply pressure orally to the filler neck and found the gas cap leaked as if it was an open vent is when I realized I needed the factory jam part filler neck… and that’s how I got my check engine light off and cleared for inspection

I may have a leaky tank hose or breather. My gas cap used to go "pshh" when i removed it. No more. Evap solenoid alows flow when energised. Blocks flow when disconnected. I just unplugged it and the breather line. I no longer smell gasoline either when i stop. Gas mileage went up 5 mpg... I believe it was sucking lots of air through the tank somehow.

Great video and explanation! Question! Can a evap vacuum leak, have enough effect, on the rest of the vacuum system, to cause the transmission to code and shift a little hard? I found my vacuum leak to be at the base of the filler neck on our 2004 Colorado!

Great tone for teaching Bro! Keep up the great work!

Very simple and clear for eveybody that has some cars knowledges.Great job and thank you.

A concise yt video that explains what I needed. Didn't know that was a thing. Great video!

Wow! Great explanation. Less scary than I thought.

Glad i ran into this video, very informative and easy to understand.

Thanks for the video, employer asked me if I knew about Evap systems this video got me up to speed lol

your amazing calm soothing voice tone makes the audience understand and absorb information very easily. great teacher and presenter

I got that dam engine light on, went to Auto Zone and got a report. P0443 your video helped me to understand thanks.

By far the best video on this issue I have ever seen

Thank you thank you thank you so much for this video. I've been fighting this evap problem for 2 and 1/2 years and now I finally understand it

Woow you broke that down 101 lesson Thank you for the information 👍

The explanation was crystal clear thanks.

This video *really* helped me understand the evap system! Thanks

Exactly the video i needed. I think im having EVAP issues. The theory in the video is explained perfectly so i can understand how EVAP works.

Very easily and clearly explained. Thank you

Thanks for a good down to earth explanation and ideas for fault finding.

Excelente explicación, muy acertada y exacta, muchas gracias.

Just replaced my purge valve on my 4th Gen TL. I love your channel BTW

Thankyou, I have a large emission leak on my 2020 Buick envision…. Can’t get in unti Dec 6th…. My car never had a gas cap only a door

Thank you for this video! I got 97 W140 Benz and recently I got P0455 error and CEL. I'll try to check both purge valves (this car has two of them) and the gas cap. Other stuff I can't even touch since my garage is pretty narrow. Unfortunately, the charcoal canister is located behind the rear wheel liner. Can't even register the car while this CEL is present...

No one explains mechanical work like 1Aauto!!!!

Your explanation was clear and good. Keep up the good work

Awesome video. Really explained the EVAP system well so I can start to have mine diagnosed and fixed.

Great video! What if your vehicle doesn't have a gas cap?

Thanks a lot u are a real teacher 👍👍👍👍

ive replaced the purge valve years ago and now the gas cap today and at some point the vent valve today. Hopefully this does the trick or else its the connector for the damn purge valve thats causing it to stay open.

The purge valve and related system is easy to understand, when it opens the fumes are vacuumed into the intake stream. Tell me more about the vent: does it just vent to outside air or is it terminated in the system somewhere? Your diagram doesn't show exactly what it does.

Happy Christmas 🎄 Thanks 👍 From Nick Ayivor from London England UK 🇬🇧

Thanks for the good video. Very clear, and now I understand. Have a blessed day.

i love thos type of videos 1 a auto parts good work

Very clear and accurate! Thank you so much!

Well done... Great informative video.

Best and clearest explanation You rock

Thanks so much you all are the best I asked for a video about this and here it is thank you thank you

I read that habitual 'Topping Off' your fuel tank can eventually render the charcoal canister ineffective. If this occurs would it cause an EVAP code?

Thank you!! Just got the code today and now i know what to look for.

Would you get the same code for a bad gas cap as you would for a faulty evap canister?

thank you for taking the time to explain everything!!!

For a couple weeks, I smell gas in my garage. There are no leaks under the truck. Would a problem in the system you describe cause this gas smell? How about a bad/cracked canister? What are the first things you'd check?

Forgot to mention about the “evap pressure sensor”. Bad evap pressure sensor could also cause an evap code if it’s malfunctioning. But good explanation.

Good job my friend

Great explanation. Thanks so much.

Awesome thank you. My vorvette has a code for blocked vent . Replaced the vent solenoid, and still has the code come back.

Great explainations. Thanks !

Great explanation. My 2015 Mini F56 B38 engine has code 190302: "fuel tank ventilation air system micro leak; leakage greater than 0.5mm". Symptoms: rough idle, and noticeable shaking while driving and longer start up after refueling (~5 seconds). Ordered purge valve hoping it will fix the problem. Let me know if anyone thinks it's something else, but I'm starting with purge valve since it's easier to access. Next on my list are the leak detection module and vent valve.

My brother just called me about his evap system on his '14 Ram 1500 having problems. I asked him if he has a habit of constantly clicking past the automatic shutoff while at the gas pump. He said yes and I told him to tell that shop you do this so they know what to look for. Then I told him he only needs 1 or 2 clicks not 20 past the automatic shutoff.

This is just perfect explanation!

One thing I did to help find leak after spraying everything with soap and water is I duct taped gas cap opening after removing the cap. Poked a little hole used compressed air in filler neck

Great, clear and helpful video. Thank you.

most clear explanation I every read for P0455!!!

Thank you for this detail. What a kind of signal electric to command valve of purge ( it is square wave or analog wave

could a vent valve hose clog cause pressure to rise making it difficult to fill the tank creating a check engine light and hesitation near idle? Your awesome!

Very informative and helpful. Thanks for sharing.

very, very helpful. GOD BLESS YOU. thanx !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Great explanation, does having the gas tank full mean the engine light is less likely to come on or more likely to come on?

Enjoyed your video. Great explanation of P0455 code. The check engine light on my 2014 Prius came on with the P0455 code. Upon checking I discovered my air filter was missing. I believe it was removed and not replaced when my oil was changed about a month ago at a local oil change service. Would this cause the P0455 code?

You made it clear that the purge valve and vent control are in 2 different locations but are they the same part? I can only find vent control replacement on your website for 2012 altima 3.5

Persistent P0455 code. Replaced gas cap twice. Looks like I’m going to have to try the “replace until it’s fixed route” to find the issue. No access to an evap smoke machine. What, after the gas cap, is the next thing I should try? I do have a faint gas smell. 2007 Tahoe.

Okay so 2 questions.. Would a blocked purge vent affect gas mileage at all? And also, does this cause rough idling?

Thanks you explained how the system works

iHave a 2013 GMC Sierra & Got The Code PO446 , replaced the Charcoal Canister & truck is now getting gas quick into the tank without it stopping on its own

I stopped over filling gas tank to top of neck. No more codes. Fuel was entering canister.

Good stuff, thanks for making this simple

My Charcoal canister was putting charcoal in my purge valve which was stopping at up so I took the charcoal canister off and install a new purge valve.. do I need to keep the hose in from the charcoal canister or can I take it off

Excellent explanation!

Did I, add the - turbo fan - coolant down below? Any pre - in evaps =: cooler than factory.

Can i just block off and delete the purge valve? I want to clean up the engine bay

I’m about to get ripped off. This video helps me understand what I know is going on. Problem? I have car sitting at dealerships service department. They want over $30++ to do testing… Where’s a at home mechanic

Hi. Good explanation.But you didn't mention the"LEAK DETECTION PUMP" which is part of some evap systems...

Outstanding Brother ... great presentation

thorough explanation 👏 nice

Very useful video 👍☺️

Even I understood, thank you for making this video.

If I found lil black charcoal pebbles in Purge Valve Solenoid, is that from the purge valve canister or from the charcoal Vapor Canister? Thanks nd great video!

Would this apply to older and newer vehicles as well?

I have a P0440 large leak in my 2004 sequoia. I’ve changed the canister and components on it. I can’t figure what it is

How do you know how to test if your fix worked? Do you need a fancy scanner to get live data? Do you just delete code and wait to see if it comes back? Is there any live data I can check to see if the problem is resolved?

Which one of these problems would make it so that it’s hard to fill the gas tank? The pump keeps shutting off on my Subaru