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Check Engine Light? Codes P0446, P0455: What Causes a Car EVAP Code? - YouTube
Channel: 1A Auto: Repair Tips & Secrets Only Mechanics Know
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so you're driving along and your check
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engine light pops up you scan it and you
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find that you have an evap code what
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does that mean first you need to know
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what the evap system does it's part of
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the emission system that prevents fuel
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vapors from entering the atmosphere here
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is how most of the systems are set up
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some components may be in a different
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structure but the basics are the same
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you all have the fuel tank and you have
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the fuel vapors you have a gas cap you
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have the e bap cannister you have an
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evap vent and you have a purge solenoid
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and then this would be where it connects
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to the engine on the intake side and
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also there may be a pressure sensor in
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the fuel tank different vehicles have
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them in different places sometimes they
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may be over in this line or part of the
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vent when the car starts and it wants to
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engage the evap system what it's going
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to do is send power and ground to the
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vents which is normally open and it's
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going to close that vent and the vapors
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are in this area you want to keep them
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out of getting out of the gas cap
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they're going to go through the charcoal
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canister but we want to put a vacuum on
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this system so the computer is going to
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command on this purge valve which is
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going to open normally the purge valve
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is closed that will open and we're going
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to have a vacuum going towards the
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intake and it's gonna pull the fuel
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vapors into the canister this valve will
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be closed at the time
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and it's going to monitor the vacuum in
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the system
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to make sure that you don't have any
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leaks this will close eventually and
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with the vacuum in the system the
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computer is going to monitor how long it
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can hold that vacuum and if it can't
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hold the vacuum then you're gonna get
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your check engine light so if you have a
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leak the first thing you want to check
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is the gas cap unless you have an evap
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circuit code it's always best to start
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at the gas cap just grab the gas cap try
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to pull on it to see if it's completely
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loose and then loosen it up check the
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seal see if it's dry rotted if it is
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it's gonna need to be replaced and also
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check the ratchet part of it if it
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clicks or if it doesn't click however
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the gas cap is set up if it's really
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loose then it's probably not tightening
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down and you could have a leak there the
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other two problems that are pretty
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common on most vehicles because they're
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the only moving parts in the system is
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the vent and also the purge valve most
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vehicles the purge solenoid is going to
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be somewhere near the intake it'll be a
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valve like this it'll be wires connected
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to it this hose goes to the back of the
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vehicle and this hose right here goes to
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the intake itself one way to test if
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this valve is actually closing you can
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take a vacuum pump put a vacuum on it it
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should stay and it looks like it's
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holding which is good if you have the
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ability to take the scan tool and open
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the valve you can plug this back in have
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the scan tool open the valve and see if
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it goes just to zero somewhere near the
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fuel tank you're gonna have the EVAP
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canister or the charcoal canister it's
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located right here and near that is
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gonna be the vent valve to check that
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the best way to do it is to command it
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on and off with a scan tool and see if
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it opens in
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so these are the three most common
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problems to purge valve the vent valve
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and the gas cap those are the three
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moving parts these other components you
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could always have a leak in the gas tank
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if the fuel pump or anything is rusty a
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lot of times those are gonna leak it's
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hard to find a leak if it's not one of
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those items you can be creative
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sometimes soapy water works if you spray
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something down it's gonna be hard to
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pressurize it but I've seen just the
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natural pressure of the gas tank cause
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bubbles from the soapy water so that's
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one way when at the dealership or most
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automotive repair places they use a
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smoke machine and they pour smoke into
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here and try to find the leak it's not
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that easy to find that way either but be
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creative take a look at any of the lines
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and just see if you see anything obvious
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that's the most easy way to do it I hope
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this video helped you out
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understanding how evap systems work if
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you enjoyed this video please subscribe
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