greetings viewers here at the car guy
here with trq where you can view before
you do in today's episode we're going to
be going over the check engine light
codes P0456 P0455 and p0442 these codes
pertain to evaporative emission leaks on
the fuel tank side of the system and
whenever I get one of these codes this
is where I usually start at the gas cap
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and the most common cause I see of
evaporative emission leaks on the fuel
tank side is the fuel cap and you want
to make sure that when you're filling up
your vehicle that you tighten this all
the way and it usually three clicks
fuel caps can also go bad over time so
the fuel cap itself may be leaking or
there may be some debris between the
fuel cap and the filler neck any of
these things can cause a leak in this
area this is why I usually go here when
I'm dealing with evaporative emission
leaks like this I've retrieved the codes
from this vehicle and it has a code
P0456 before we get too deep into our
diagnosis of the evaporative emission
system I think it's important to know
what that system actually does in your
vehicle if you take some gasoline and
leave it sit out it will eventually
evaporate and that's actually
hydrocarbon emissions which is not good
and something we want to prevent also
it's fuel loss so if you're just sitting
there parked and your fuel is
evaporating you're not getting a chance
to use it so you can drive down the road
so the evaporative emission system what
it does is it takes those fuel Vapors
that build up inside the fuel tank and
sequesters them inside of a charcoal
canister until such time as you're
driving down the road and it can release
those Vapors back into the engine to be
burned and consumed so that's the whole
reason why you have an evaporative
emission system to begin with and it
monitors itself for leaks and when you
get a code for one well it usually means
there's some leak in the system that
needs to be addressed
foreign thing to do if you have one of
these codes is a good visual inspection
of the system at the areas around the
charcoal canister but in particular the
filler neck I've removed this rear wheel
and also the cover that was over this
this can develop corrosion in this area
and if it does it can cause those small
leaks that would set that code so if you
can put your eye on the filler neck and
all of its connections and make sure you
don't see any problems while you're
doing your visual inspection keep in
mind that you're looking for a fuel leak
so in addition to looking for any damage
to the evaporative emission system also
smell you can smell fuel if it's leaking
so if you smell fuel anywhere around
this area you know you've probably got a
leak in that system continuing on with
the visual inspection this is the
charcoal canister on this vehicle these
are usually located someplace near the
fuel tank they have a bunch of lines and
hoses going to them do a good visual
inspection on all of those to see if
there's anything broken or damaged if
there is repair it that could be the
source of your leak
continue our visual inspection with the
charcoal canister on the bench and just
look around for any damage that you
might see on the outside of it this
lives under the vehicle so if you hit
some road debris or something like that
it can come up and hit this and possibly
damage it this side is the charcoal
canister
this is the sensor that measures the
amount of vacuum or pressure inside of
the system these are manufacturer
specific as far as testing is concerned
because there's going to be a five volt
reference there'll be a ground and then
there'll be a signal wire coming out of
it so I'm not going to show the testing
of that if this is an issue there's
normally a code just for the sensor what
we're going to do now is the canister
vent solenoid and what this does is if
you when the system activates you need
to allow fresh air to come in to allow
the vapors to come out so you can't just
try to run the vapors out it's like when
you put your finger over a straw and
lift it up out of a drink all that drink
stays inside the straw until you move
your finger well basically this valve is
moving the finger and we're going to
test that now to see if it's sealed you
can see that this wire goes from this
connector up over here to this solenoid
so we can actually plug into this part
I'm going to test this entire wiring
harness and the solenoid all at the same
time by testing down here instead of up
over here
going to take a vacuum pump which I have
here that I'm going to insert into the
back here
and then
um I'm going to be using a Power Probe
but if you can supply power and ground
to this solenoid you should be able to
activate it like I'm going to do here
so there's two
connections on the inside of it
well first let's just see what kind of
vacuum it's able to hold
so with it just hooked up
and the solenoid is not activated
it doesn't hold any vacuum doesn't
produce any vacuum but when we activate
the solenoid and do this
Supply Power you can feel it a lot of
times you can hear it click
and I can also feel it so if I don't
feel any activation when I do this this
could mean that the solenoid is bad
right from the beginning but I'll
activate the solenoid and I'll apply
vacuum to it
and then it should hold vacuum
this has been holding vacuum for a good
amount of time now and I think we can
reasonably conclude that this solenoid
is good when we activated it it held
vacuum when we didn't activate it it
didn't hold vacuum so that says to me
it's doing what it should but if it was
leaking down slowly then that would
indicate a problem likely with this
valve and you need to replace it but
given everything that we've seen here I
believe the problem was a loose gas cap
but I'm hoping this testing was
something that you can use to see if
your evaporative emission system is
working properly after you're done with
your testing make sure you hook all the
lines and connections back up otherwise
you could end up creating a problem that
you didn't have before now that we've
completed our inspection of the
evaporative emission system in this
vehicle I believe it was the gas cap was
the cause it wasn't quite tight when I
first checked it so I'm going to clear
the codes now but it may take a while
before I can say that this vehicle is
fixed because these codes don't set
right away if there's a problem it has
to go through a few drive cycles so
drive it around for a couple of weeks if
you've got no check engine light after
that you're probably good if you do well
you can go back through what I've shown
you in this video and hopefully you'll
be able to find the problem but for now
let's clear the codes
some scan tools have the ability to
monitor the evaporative emission system
and this one does
so in order to verify your repair you
can sometimes run a test with the scan
tool like this one just did
I believe we've fixed this one
evaporative emission leaks can be
difficult to track down normally what I
would use is what's called a smoke
machine where you run pressurized smoke
into the system and you look for the
lease that way that can be helpful but
that machine's very expensive and I
didn't think many of you out there might
have one so I tried to show you methods
without a smoke machine in this video
and I hope that was helpful to you there
will also be additional information down
in the description so check there if you
have other questions I'm Eric the Car
Guy here with trq be sure to view before
you do thank you so much for watching
today be safe have fun stay dirty I'll
see you next time
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