Check Engine Code Says EVAP? How to Diagnose EVAP System Problems and Leaks

Did you get a check engine code referring to the EVAP system, but not sure how to proceed? Watch this video! Andy points out the most common parts that trigger EVAP codes in your car or truck. He also gives you tips on how to diagnose and repair those problems. He takes a look at the gas cap, the EVAP purge valve, and the EVAP vent solenoid valve. All of these parts exist in modern vehicles with emissions systems!

For more great diagnostics that you can do yourself at home, check out this playlist!

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While 1A Auto strives to make the information provided in this video as accurate as possible, it makes no claims, promises, or guarantees about the accuracy, completeness or applicability of the content. No information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. All do-it-yourself projects entail some risk. It is the sole responsibility of the viewer to assume this risk. 1A Auto is not responsible or liable for any loss damage (including, but not limited to, actual, consequential, or punitive), liability, claim, or any other injury or cause related to or resulting from any information posted in this video.

[chepitok]

Most videos just show how to replace each part but don't show how it's all connected. I've replaced my gas cap twice and was about to replace my purge valve. Now I can look at everything and make sure there's no visible problems. Much appreciated 🙏

[randyd]

This is by far the most complete video on the small evap leak that I've seen so far. I was thinking I might fix this myself cheaply but not so sure I can fix it OR that it will be cheap. At least I know a few more things I can look at, but I may have to take this in since I really don't have the time, tools, or inclination to fix this myself. I did buy a new gas cap and that did shut this off for a little while then it came right back on. I did not notice if there was any rust build-up there so I will check that now.

[alexandercahoulan]

Usually I severely dislike 1A auto but this guy and Sue are the best and they legitimize the channel. In my humble opinion lol

[pelqui]

With such a good video like this, I saved me thousands of dollars going to the dealer / shop. Greatly appreciated.

[michaelpalmer]

Your videos have helped me to move forward in my automotive career and I greatly appreciate the content.

[bryanavila]

Also don’t buy aftermarket fuel caps. Use oem parts. Thank me later 😎

[walter.bellini]

Thank you for the video, beautifully done, and good info pushed out
Suggestion is to make sure that you check the rubber hoses around the Purge Valve, especially if your car is older as the rubber gets hard and begins to crack. If you have a vacuum gauge, test out the purge valve on the exit side NOT the intake side where the fumes come in, test to see if the output portion of the valve hold vacuum if it doesn't then that is part of the problem, buy a new OEM valve, avoid aftermarket ones for the long haul. I am going through this on a 2008 Lexus ES350, working the issue through, but can't easily get to the canister in the back as it is buried and not easily to access without a real lift which I don't have. Thank you

[raelmacintyre]

Would an EVAP leak cause hard starting?

[mironkorzalko]

My dealer wants to replace the entire assembly when just the cracked hose you showed is chewed up....what's a good replacement for that rigid contoured hose?? I'm not paying 1000 dollars for 10inches of bad hose.

[clearblueswamp]

For anyone having recurring issues with the Evap code coming on and not passing inspection, Change out the pressure switch on the tank, it's in the same harness as the Evap, and will cause the light to come on, although the switch is basically for hard start, If there is a glitch in the switch, It triggers a Evap code, I have found this in numerous other cars, And for under 40 for the switch, its not worth the headaches, Believe me you will be happy you did, Enjoy your new sticker,

[JuanGomez-gbce]

Hi very informative video. I have a 2016 Corolla with strong fuel smell coming from AC vents first 1-2 min after being started in morning, then clear normal air and no engine codes. Any idea of what could be my issue?

[MrHeHim]

If its a rather dry engine bay, no oil leaks. I just look for 'wet' vacuum lines. When the car is off the oil in the lines will soak the area the leak is in 😉

And if everyhting is clean, then i start checking like in the video above 😁

[iranmatias-quinones]

I greetings. I have 2010 dodge charger code 0455 . Did smoke test, saw leak at the canister. Better known as the " fuel vapor leak detection pump filter". Strange but true.

[grominwithrob]

I had a bad purge valve that simulated a vacuum leak with no codes. Caused 1-2 random misfires on random cylinders. Caused the truck and transmission to operate like pure crap. Fuel trims where horrible. I figured it was an internal leak because propane on a cold started engine didn’t have any effect. Brake booster was fine so it really narrowed down to the purge valve quickly so I checked it out. It was stuck open. Replaced it and did a fuel trim relearn and it my truck is running and shifting great again.

[paulraven]

How do I know if it's the purge solenoid under the hood or the vent/whole canister assembly? I'm just guessing and don't have a high level scan tool.

[ro-landocalrissian]

I’m curious is the code for an evap canister the same as the code for anything else including a gas cap problem?

[toml]

Help me understand this: If the engine is off, the vent is open? Does that mean the gas tank is venting into atmosphere? Is there a one way valve in the vent line to keep this from happening? I don't smell gas fumes wnen wandering about the car so I assume the gas fumes in the tank are not escaping even on a hot day. Am I correct in assuming the round canister next to the vent valve is some kind of filter? How much pressure can build up in the gas tank? I know, too many questions.

[Blueflyer]

I heard over filling the gas tank on my forerunner can Cars and evap system problem is that correct?

[biggabe]

I have a p0446 on 2001 chevy tahoe. I changed purge valve, ventilator valve, and gas cap. Check engine light came back on. Only thing I haven't done is the charcoal canister.

[Journeyman-Fixit]

On my 2003 4.3L GMC Sierra I replaced both purge valves (front and rear) and after putting a smoke machine on the system there where no leaks BUT I still get the P0442 / P0449 codes??? I am going to try replacing the charcoal canister next.