Apologies for the resurrection. As with many others I too have the issue with the code. It actually came back this morning. Picked up another gas cap and so far still have it. So am about to embark this path you described above.

Some things I have noticed in my situation.
This seems to happen more often in the cooler months. Which is good b/c I have to get emissions done in the summer. Fortunately have that covered for another year, but it seems that the problem is starting to creep back after a few months off.

Also, my caps never have pressure anymore. I always click them multiple times past. I never get that 'psssh' when opening it up for a refuel. I also never top off.

Makes me wonder if is a problem at the purge valve on the stank being stuck open. Time to get a vacuum pump and get dirty.

Good luck dude. I still have yet to mess with mine anymore. Life!! Here's a link to another thread I started several months ago about the same (or very similar) issue. Maybe something in there will help as well.

EVAP codes after replacing fuel pump

Ok, I had a p0456 and reset it after inspecting the gas cap. It came on again this time with P0456, P0455, and P0441. I started with the VSV purge solenoid at the engine bay. It holds vacuum one way but not the other, i.e., putting a vacuum on it from the manifold side it held fine, but putting a vacuum on it from the tank side would not hold more that 12 mmHg and even then it slowly dropped (my MightyVac vacuum pump goes to a bit over 25mmHg).

If i understand correctly, the check routine in the night is for it to close the VSV purge valve (its normal state) and the VSV vent valve at the canister and then create a vacuum in the system. That leaves only the two valves or the gas cap to be obvious leak spots. With the VSV purge not holding a vacuum from the tank side of the line that seems to be the obvious solution.
Or have I missed something

I do note that all the vacuum hoses in the bay are getting brittle and such. Is there any harm in using ordinary vacuum line of the right diameter as opposed to buying the preformed replacement hoses? I will go ahead and do the engine bay and canister connections with new vacuum line if it is not an issue.

Jeff you also have a big rubber hose from the gas door/neck and the tank.

Where is the little pump that is used in the self-test? What would happen if you disable this pump and the self-test could not run?

I love how you refused to really spend any money and still fixed this issue, pretty funny haha

Here is my VSV Purge valve. on the manifold side it will pull 25 inches of HG and hold it steady. However, on the tank side it will not let me pump it above 15 inches HG and it drops fast. I understand that the valve SHOULD hold vacuum both directions, right?

Manifold side holding steady at 25 in. HG




The tank side failing to hold vacuum

Thinking about the vapor system operation, I suspect my VSV Purge at the engine as it fails to hold vacuum as set out above. If I disconnected the line at the bay and capped it overnight, then when the ECM runs the purge cycle where it seals both VSVs and then creates a vacuum in between, if my ONLY problem is the purge VSV and/or the flexible lines in the bay that would bypass it. So if I got NO MIL in the morning it woudl be some evidence that the rear end of the canister system was operating OK, right?

At least i could do that while I await the shipping on the new vsv purge. :-)

Need someone smarter than I am here. I pulled the VSV Purge from my 2012 Camry I4 and it exhibits the same behavior as the one on the 2008 4Runner i noted above, i.e., it holds 25 inches Hg on the manifold side, but wont go above 15 inches or so on the tank side and slowly loses vacuum down to like 8 inches or so. Now I am really confused. If the purge cycle is the ECM closing both VSVs and inducing a vacuum between them and seeing if it drops, how can that happen if both the vehicle's VSV purge exhibit the behavior in my video a few posts ago?

I had thought it was the purge VSV and have one ready to order. Now I am not so sure. Help.

That it falls on the tank side seems strange. I tested mine with it in place through the hose that goes to the hard line on the frame. In this case, it now holds vacuum (similar to pictures earlier in the thread). Initially, it did not, but the hoses were in bad shape and now have been replaced with high-pressure fuel line.

Maybe this is an inconclusive test as the surge valve is in series, but I believe that the test pump & sensor wouldn't see any different from the hard line than what I tested. I.e., test it in the same manner that the automated cycle is testing it.

FWIW, using a Mityvac, I believe that my system is really holding vacuum everywhere and that the system is not leaking (like the OP, I also replaced the line from the EVAP filter to the tank). However, the light keeps returning, so I'm clearly not an expert on this yet either.

SOrry all, i had not seen any updates on this thread (what do I do about that, subscribe everytime?)

if its hold at 15, i'd say thats plenty to expect. more than that and your literally sucking open the gate.

If I can help more, give me a nudge.

Thanks for a great thread. If you don't mind, from where did you pressure test the tank? I had questionable lines at the surge valve (replaced with BMW fuel line) and a deteriorated line from the evap canister to the motor (also replaced with BMW fuel line). The system holds vacuum from the evap hose to the motor and the evap canister itself holds vacuum. I feel that this means that one of the big plastic lines or something else in the fuel supply.

I couldn't find any Toyota part numbers for these o-rings, so they appear to be "part of assembly".

Did you just find something big enough to jam into the plastic line from the evap canister to the tank to vacuum test it?

Thanks!

Its bee n a while so Im a little foggy, but you should have a rubber hose from the tank to the Canister, and it has plastic ends. I think I lucked out and jammed a hose into the plastic fitting to test it. i never had to change those little o-rings in the plastic ends. Just make sure the those plastic fittings are clean inside and fully seated

so had my emissions checked 3 weeks ago, passed,
then a week later my engine light comes on and VSC turns off.
Took to my mechanic of 20 years and tells me I need to replace charcoal canister and it costs $950.
Mechanical manually inspected it and said the valve wont budge and there
is an emission leak.
WTF toyota.....

2008 V6 4runner sport edtion, 64k miles

I woult test the valve yourself. Basically you can jump the connector with a 6v battery and some paperclips. which pins is detailed in the service manual.

I'm not distrusting you mechanic, but its an easy thing to not test right, especially without the factory service manual. These dont exactly fail often. Unless your top off your tank way too much I suppose.
Also read my previous link in the toyota emmisions system.