Anatomy of P0456 - Small Evap Leak (1 Viewer)

[TeCKis300]

Recently have been getting CEL code P0456 - small evap leak.

As the evap system self test is performed at night by the vehicle, usual symptom would be a nice greeting in the morning with flashing CEL, 4LO, TRAC, etc. And the inability to toggle 4LO, CDL, etc., if off-road camping. It progressed over a couple years from rare blue moon nuisance, to continuous every other day. Got really good at using a BT OBD-II dongle to reset in 30 seconds. Interestingly, after many many resets (maybe 30+?), the car will throw like 8 EVAP CELS, then stop complaining on the dashboard, and just keep the internal code. But in order to do CA smog, it needs to be fixed.

I did a bunch of sleuthing and tests and isolated it to no particular external leak, but an internal failure of the Evap Canister (aka charcoal canister). To be fair, there's many ways a small evap leak can manifest. From a simple gas cap seal either not tightened or worn. Or compromised connection or rubber hose leaking externally. Or leaking purge VSV up at the motor. I wanted to be sure it wasn't any of these before I took the effort to drop the aux tank to get at the charcoal canister.

Today, I confirmed that it was indeed the vent VSV integrated in the charcoal canister:

The Leak Detection Pump Sub Assembly is mounted to the charcoal canister assembly by 3x 10mm hex bolts. This sub assembly includes the problem Vent VSV, which is clearly corroded. Before tearing it apart, I tried to jump it, and it was moderately clicking, but did not seal the vent.

The new charcoal canister fixing the issue also confirmed this as the problem.

Big question for me is why did this occur? What is the real root issue?​

Plausible that fuel overfilled the evap canister at one point. I'm not as sure of this, because I'm a conscientious owner and don't tend to fill my tanks like that. These components are also made to handle fuel and fuel vapor so they should be designed not to corrode with fuel.

So water/moisture?

Whenever I've experienced issues, first thing that comes to mind is modifications. OEMs spend millions of dollars for environmental, field, and durability tests, especially our vaunted LC. I have an LRA aux tank. There's various plausible reasons but the thing that I suspect is the external breather that is modified with small exposed mushroom filter on the end of a high mounted hose.

Could water be entering from that?

 

[TeCKis300]

LRA breather...

I suspect that it's this for a couple reasons. I know of at least one other member that has experience a charcoal canister failure/replacement, that also has an LRA. @Markuson Design issues like this won't only manifest once, and I wonder if other LRA owners may experience this? Then again, charcoal canisters do get old, and there's rare cases of completely stock rigs that do need to replace them

The LRA breather is setup with a simple external filter. The breather is normally open and breathing in. The area here immediately behind the tire is incredibly dusty and dirty, even with full fender liner plastics in place. Enough that I suspect with rain, enough moisture can be sucked into the evap system to create the corrosion. I'll have to toy with this, and maybe hanging the mushroom upside down will be enough to reduce water intake? May bite the bullet and plumb the breather up to the engine bay/fender area.

I've replace the mushroom filter before and it surely seems the silt caked there has seem water/moisture

 

[TeCKis300]

Possible fix options...

I replace the charcoal canister with a 200-series specific charcoal canister. Was fortunate to get it just over $500, but they are regularly closer to $800.

77740-60471​

2008-2011 2013-2016 Toyota Land Cruiser - Vapor Canister​

$512.95​

There may be cheaper options but as my fitment with the LRA aux tank is super tight, didn't want to risk a part that had different dimensions. The Tundra canister is a different part number and can generally be found easier/cheaper. I suspect it's only different in brackets and would drop right in with the existing cruiser brackets.

Another option may be to source just the vacuum VSV pump. These were available OEM for limited Toyota models but they look to be exactly the same form/fit. At about $250?

Just seeding idea in case someone later wants to try.

 

[RET2]

Possible fix options...

Rear mounted schnorkle? Sorry couldn't resist. Kudo's for the dissection and explenation of the unit.

 

[paulunm]

How did you narrow down the leak to the evap canister, and not a slight leak in an evap line?

DId you smoke test?

 

[TeCKis300]

How did you narrow down the leak to the evap canister, and not a slight leak in an evap line?

DId you smoke test?

Yes, did several rounds of various smoke and pressure tests at different points. Challenging with the LRA aux tank covering a lot of access.

 

[Markuson]

LRA breather...

I suspect that it's this for a couple reasons. I know of at least one other member that has experience a charcoal canister failure/replacement, that also has an LRA. @Markuson Design issues like this won't only manifest once, and I wonder if other LRA owners may experience this? Then again, charcoal canisters do get old, and there's rare cases of completely stock rigs that do need to replace them

The LRA breather is setup with a simple external filter. The breather is normally open and breathing in. The area here immediately behind the tire is incredibly dusty and dirty, even with full fender liner plastics in place. Enough that I suspect with rain, enough moisture can be sucked into the evap system to create the corrosion. I'll have to toy with this, and maybe hanging the mushroom upside down will be enough to reduce water intake? May bite the bullet and plumb the breather up to the engine bay/fender area.

View attachment 2950004

I've replace the mushroom filter before and it surely seems the silt caked there has seem water/moisture

View attachment 2950005

All good items to check to be sure.

Unfortunately though… -My evap codes, boiling gas and charcoal cannister failure happened well before I had the LRA. I replaced the cannister at the same time as the LRA install…since it would be difficult to access after (crazy expensive for what it is, too) and sadly…within a few weeks…my evap codes reappeared.

That was in 2018. At that point, I basically resigned myself to zapping evap codes—which typically show up when my main tank is about half full…in the morning.

My little workaround makes it super quick to deal with…albeit still annoying. -I installed an OBD2 extention cable that also has an on/off switch so I can keep a small, wired reader/reset plugged in and ready. That way, my reader isn’t eating my battery—which they can and will do if left plugged in normally.

I’ve got it down to a science (haha) and can even do it after start-up if in a hurry. It takes me about 12 seconds.

Still… Its annoying and reminds me of Toyota’s silly level of the function-crippling of needed function due to unrelated sensors (like no 4-Lo if you don’t clear an evap code…).

 

[TeCKis300]

All good items to check to be sure.

Unfortunately though… -My evap codes, boiling gas and charcoal cannister failure happened well before I had the LRA. I replaced the cannister at the same time as the LRA install…since it would be difficult to access after (crazy expensive for what it is, too) and sadly…within a few weeks…my evap codes reappeared.

That was in 2018. At that point, I basically resigned myself to zapping evap codes—which typically show up when my main tank is about half full…in the morning.

My little workaround makes it super quick to deal with…albeit still annoying. -I installed an OBD2 extention cable that also has an on/off switch so I can keep a small, wired reader/reset plugged in and ready. That way, my reader isn’t eating my battery—which they can and will do if left plugged in normally.

I’ve got it down to a science (haha) and can even do it after start-up if in a hurry. It takes me about 12 seconds.

Still… Its annoying and reminds me of Toyota’s silly level of the function-crippling of needed function due to unrelated sensors (like no 4-Lo if you don’t clear an evap code…).

Yeah, it's what I was doing as well until now needing to smog so I'm biting the bullet.

Am I understanding that you continue to get evap CELs after changing the charcoal canister? What codes?

 

[Markuson]

Yeah, it's what I was doing as well until now needing to smog so I'm biting the bullet.

Am I understanding that you continue to get evap CELs after changing the charcoal canister? What codes?

Can’t remember… I’ve posted them before, bit its been a while. Usually 3-5 codes trip prior to clearing.

Regarding smog— The good news is… Evap codes do not persist once cleared and are no orob. I’ve passed smog several times now despite this annoyance.
Also… For anyone with a “secondary air” failure code…that is the one related code that does NOT disqualify a CA smog test according to my smog guy.

 

[TeCKis300]

Looks like I never finished this thread.

Replaced the charcoal canister. Then modified the LRA breather to high loop it to discourage it from pulling in water. Tear down evidence shows corrosion in the vent valve.

Corrosion shows signs of water ingress

View attachment 3093949

 

[clrussell]

Looks like I’m in the same boat. I guess I’ll pull apart the evap canister sometime..

Po456 and Christmas tree dash upon startup recently.

Really just need time to fully diagnose it. Who knows when that’ll be. Until then at least I don’t need 4 lo and can clear it

 

[isthatalexus]

Since this is one of the most advance Charcoal Canister threads, I'm posting this here.

Equipment: 2008 LC200, 24ga LRA, just-installed OEM fuel pump in main tank, replumbed poor PO LRA installation, tripple-checked all work.

Observations:

• LRA makes a noticable 'gong' sound after short drive, and another after parked. Either pressure or vacuum is the cause. Judged vacuum based on gas cap behavior.
• Also hear what must be purge pump on CC run after vehicle is turned off.
• Outrageously low MPG at low speeds and idle. (might be other issue, but MPG indicator drops 0.1-0.2 per ~15 second interval while idling at traffic light)

Process:

• re-re-re-removed LRA
• rubber glove fingers zip tied over all fuel in/outgress points
• removed CC for further Dx

Question:

• how much does a new Charcoal Canister weigh? I'm pulling 7 lb on fish scale (relevant for dx in case it's carrying a bunch of fouled/gooped fuel residue; can hear media shaking inside, but no way to know if all of it is good, or partially fouled)

UPDATE: rediculous. As I'm writing this and reviewing photos, before posting, I find this (see pic)

yes, that's a bent pin on the CC harness connector. Pretty great. LOL. [...breathe...]

But I still want to know weight of clean CC, if anyone has measured. (shipping weight tends to be unreliable)

 

[tbisaacs]

Since this is one of the most advance Charcoal Canister threads, I'm posting this here.

Equipment: 2008 LC200, 24ga LRA, just-installed OEM fuel pump in main tank, replumbed poor PO LRA installation, tripple-checked all work.

Observations:

• LRA makes a noticable 'gong' sound after short drive, and another after parked. Either pressure or vacuum is the cause. Judged vacuum based on gas cap behavior.
• Also hear what must be purge pump on CC run after vehicle is turned off.
• Outrageously low MPG at low speeds and idle. (might be other issue, but MPG indicator drops 0.1-0.2 per ~15 second interval while idling at traffic light)

Process:

• re-re-re-removed LRA
• rubber glove fingers zip tied over all fuel in/outgress points
• removed CC for further Dx

Question:

• how much does a new Charcoal Canister weigh? I'm pulling 7 lb on fish scale (relevant for dx in case it's carrying a bunch of fouled/gooped fuel residue; can hear media shaking inside, but no way to know if all of it is good, or partially fouled)

UPDATE: rediculous. As I'm writing this and reviewing photos, before posting, I find this (see pic)

yes, that's a bent pin on the CC harness connector. Pretty great. LOL. [...breathe...]

But I still want to know weight of clean CC, if anyone has measured. (shipping weight tends to be unreliable)

View attachment 3258737View attachment 3258741

In my professional life we call that debugging by confession. Sometimes you just need to explain it to someone else to see the issue.

 

[isthatalexus]

In my professional life we call that debugging by confession. Sometimes you just need to explain it to someone else to see the issue.

This, 100%.

Outside of lol-poasts, I would bet that 2/3 of my technical posts either resolve through DbC, or they do so shortly after hitting 'post.' Writing is organized thinking.

Please send luck and power for pin bend-back.

 

[Thomas Nelms]

Recently have been getting CEL code P0456 - small evap leak.

As the evap system self test is performed at night by the vehicle, usual symptom would be a nice greeting in the morning with flashing CEL, 4LO, TRAC, etc. And the inability to toggle 4LO, CDL, etc., if off-road camping. It progressed over a couple years from rare blue moon nuisance, to continuous every other day. Got really good at using a BT OBD-II dongle to reset in 30 seconds. Interestingly, after many many resets (maybe 30+?), the car will throw like 8 EVAP CELS, then stop complaining on the dashboard, and just keep the internal code. But in order to do CA smog, it needs to be fixed.

I did a bunch of sleuthing and tests and isolated it to no particular external leak, but an internal failure of the Evap Canister (aka charcoal canister). To be fair, there's many ways a small evap leak can manifest. From a simple gas cap seal either not tightened or worn. Or compromised connection or rubber hose leaking externally. Or leaking purge VSV up at the motor. I wanted to be sure it wasn't any of these before I took the effort to drop the aux tank to get at the charcoal canister.

Today, I confirmed that it was indeed the vent VSV integrated in the charcoal canister:

View attachment 2949446


The Leak Detection Pump Sub Assembly is mounted to the charcoal canister assembly by 3x 10mm hex bolts. This sub assembly includes the problem Vent VSV, which is clearly corroded. Before tearing it apart, I tried to jump it, and it was moderately clicking, but did not seal the vent.

View attachment 2949460

View attachment 2949453

The new charcoal canister fixing the issue also confirmed this as the problem.

Big question for me is why did this occur? What is the real root issue?​

Plausible that fuel overfilled the evap canister at one point. I'm not as sure of this, because I'm a conscientious owner and don't tend to fill my tanks like that. These components are also made to handle fuel and fuel vapor so they should be designed not to corrode with fuel.

So water/moisture?

Whenever I've experienced issues, first thing that comes to mind is modifications. OEMs spend millions of dollars for environmental, field, and durability tests, especially our vaunted LC. I have an LRA aux tank. There's various plausible reasons but the thing that I suspect is the external breather that is modified with small exposed mushroom filter on the end of a high mounted hose.

Could water be entering from that?

Nice write up on this and helpful. So I‘m currently experiencing a similar issue while driving from Austin to RedRiver. First, once I put it in Drive, it went into gear hard and then the TRAC OFF, 4-LO flashing,, Engine check light came on and it does not engage to 4-Lo?
I plugged the OBD and CODE P0456 Populated. I replaced the gas cap a few months ago. I wonder if that went bad again? Also, I read a thread about a mouse making a home under the engine-top cover. I had that happen to my 2013 and wonder if wiring was also chewed through?., And the Traction control is off, which I’d like to have ON as it’ll be icy driving home.

 

[AnyMal]

In my professional life we call that debugging by confession. Sometimes you just need to explain it to someone else to see the issue.

Also 90% of therapy.

In my case during my first year of ownership (bone stock) i couldnt get any auto fill to work at gas stations.

At the time i thought it was the collapsed filler tube problem that had been reported on MUD. In hindsight, i believe it must have been a clogged line or filter something. It has since resolved itself fully, with all pumps allowing full fill auto stop as normal and no occurrence at all in 2 years.

There is interest in an LRA group by right now, but i think i will have to go with @grinchy solution for the oem with factory fittings. Also he actually plumbed to the engine bay if i recall. Any issues there sir?

Really hope I don’t have to add this to the worry list. It somehow keeps growing…

 

[spaber05]

Bringing this back as I'm just starting to experience the P0456 code (no others codes thrown).

The facts:

2021 LC Ed Martin built, pavement princess for the most part
45k miles (second owner)
LRA small (12.5 gal) aux tank
Recently undercoated (relevant?)

P0456 comes up about a month ago, I believe, through no fault of my own (never over fill tanks or anything). I come on here, do a little light reading and replace the breather neck filter. Seems to do the job and no light for a couple weeks. Great, I'm such an incredible mechanic, *pats self on back* and all is right in the world! We can all move on, right?

Wrong: we head up north to VT for some spring break skiing with the kiddos. Almost EVERY morning I'm getting either a CEL or "Check filler cap" message. I wonder why colder/drier weather would mean a more frequent CEL vs at home in MA (maybe a 15 degree temp swing?) Any ideas why code would be thrown in colder/drier climes? Input appreciated!

 

[spaber05]

Bumping this again, any ideas on why colder temps might cause P0456 more frequently than warmer temps?

I'm at almost a month of being CEL-free and I think it has to be due to it being warmer now.

 

[TeCKis300]

Bringing this back as I'm just starting to experience the P0456 code (no others codes thrown).

The facts:

2021 LC Ed Martin built, pavement princess for the most part
45k miles (second owner)
LRA small (12.5 gal) aux tank
Recently undercoated (relevant?)

P0456 comes up about a month ago, I believe, through no fault of my own (never over fill tanks or anything). I come on here, do a little light reading and replace the breather neck filter. Seems to do the job and no light for a couple weeks. Great, I'm such an incredible mechanic, *pats self on back* and all is right in the world! We can all move on, right?

Wrong: we head up north to VT for some spring break skiing with the kiddos. Almost EVERY morning I'm getting either a CEL or "Check filler cap" message. I wonder why colder/drier weather would mean a more frequent CEL vs at home in MA (maybe a 15 degree temp swing?) Any ideas why code would be thrown in colder/drier climes? Input appreciated!

The progression with my issue of P0456 sounds similar. It was a blue moon here and there. Became more regular. Then almost constantly.

Hate to say it but the root cause is likely the purge solenoid corroding and failing as describe in post #1 of this thread. That will require a new charcoal canister, dropping the LRA, and replacement. Mine was immediately resolved after that and has been perfect again for the past couple years.

The root cause IMO is water ingress from the breather. The purge valve is generally open while operating the vehicle, with mild negative vacuum as fuel gets pulled down and pressure equalizes. This causes it to pull water vapor in rainy weather down to the charcoal canister valve.

Super important for everyone that has the LRA, or is resolving this issue to high loop the breather as in post #10

 

[spaber05]

The progression with my issue of P0456 sounds similar. It was a blue moon here and there. Became more regular. Then almost constantly.

Hate to say it but the root cause is likely the purge solenoid corroding and failing as describe in post #1 of this thread. That will require a new charcoal canister, dropping the LRA, and replacement. Mine was immediately resolved after that and has been perfect again for the past couple years.

The root cause IMO is water ingress from the breather. The purge valve is generally open while operating the vehicle, with mild negative vacuum as fuel gets pulled down and pressure equalizes. This causes it to pull water vapor in rainy weather down to the charcoal canister valve.

Super important for everyone that has the LRA, or is resolving this issue to high loop the breather as in post #10

Much appreciated @TeCKis300 - Assuming I'm not doing any real harm to the engine I might just punt this until the light becomes more constant and then do the high loop at the same time. Just disappointed this is happening in a practically new Cruiser! Also, I'm assuming none of this is covered under any kind of warranty, correct (assuming all of the above is needed)?