Code P0456 - When its not the gas cap
- Thread starter Elan750
- Start date
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
Manifold side holding steady at 25 in. HG
The tank side failing to hold vacuum
Last edited:
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.
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.
I had thought it was the purge VSV and have one ready to order. Now I am not so sure. Help.
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
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.
Elan750
New member
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
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!
Elan750
New member
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
$950 charcoal canister????
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
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
Elan750
New member
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.
What codes is it showing? P0456 alone? Other possible ones include P043E, P043F, P0441, P0450, P0451, P0452, P0453, P0455, P0500. The attached PDF shows on the second page the system and the rest tells you the EC charcoal canister cycle that runs and throws the codes. Once you get your head around it it is not too difficult. The problem is that if it is the VSV on the canister, well that is not a separately available part, so you need to get a used canister with a good VSV on it.
I went through this with a Camry some years back and the first thing i did with my 08 T4R v6 was get the schematics on the Emission Control vapor system and read them. I finally feel like I have the system understood (famous last words I am sure) If you know the code you can track the matter down using a littel testing and logic and confirm what EXACTLY is wrong and replace just that. The easy fixes are the VSV at the engine bay driver side and even the r&r with a used charcoal canister is straight forward once you drop the spare. There are other odd problems like loss of gas tank seals or broken/brittle lines and such that can be figured out.
PM me if you like and we can try to figure your issue out as even IF it is the canister, well it is not something to just throw a grand at and hope. Too many folks get new canisters and then STILL throw a code, as the mechanic, sometimes does not take the time (and it is a time consumer if you are running a shop) to do a complete evaluation of the system and make sure the DTC code and the manual diagnostics match up. Given this listing on ebay for a used one, it is SO easy to replace I think you'd kick yourself for spending a grand on it.
Hope this helps.
andreylights
New member
Sorry for resurrecting the old thread, but it seems to be one of the most appropriate to ask in.
If the system runs the diagnostic every 5 hours but I have those code come back at a very random time (first time the light came back after 22 km of driving and 48ish hours, then I drove for 4 days and 250km before it came back, then 2 days and 60 km -- its very inconsistent) does that mean that the problem is nor persistent and sometime it works while other times it doesn't? How can I diagnose the issue in this case?
the codes are P043E, P043F, P2401, P2402 and P2419.
If the system runs the diagnostic every 5 hours but I have those code come back at a very random time (first time the light came back after 22 km of driving and 48ish hours, then I drove for 4 days and 250km before it came back, then 2 days and 60 km -- its very inconsistent) does that mean that the problem is nor persistent and sometime it works while other times it doesn't? How can I diagnose the issue in this case?
the codes are P043E, P043F, P2401, P2402 and P2419.
Apologies the necro'ing this thread, but I'm in the process of trying to track down a possible leak with this CEL code. The the 3 bolts were easy enough to remove, but I'm having issues with two weird looking connections. I don't wanna break them, but they are TOUGH to do anything with and it's not readily apparent to me how they come off.
Wild Thing
New member
Thanks to Elan750 for an excellent tutorial on the EVAP system that even this rookie can understand.
After my dash lit up recently, my new code reader arrived today and similarly shows a minor leak in the evaporative emissions system. Read and cleared the codes, to see if and when it repeats. Once it does, with this thread I'll have an idea where to start. In the meantime, I know I can still drive the rig safely.
Much obliged!:cowboy:
After my dash lit up recently, my new code reader arrived today and similarly shows a minor leak in the evaporative emissions system. Read and cleared the codes, to see if and when it repeats. Once it does, with this thread I'll have an idea where to start. In the meantime, I know I can still drive the rig safely.
Much obliged!:cowboy:
Gas cap a no go for lights on issue
I’m going to my mechanic on Thursday. I need to try saving a few bucks by giving him ideas to check out. I’m on my 3rd gas cap to resolve lights being on. This time, it’s not the gas cap. I have no pressure release when taking cap off. Help, please.. thank you in advance.
I’m going to my mechanic on Thursday. I need to try saving a few bucks by giving him ideas to check out. I’m on my 3rd gas cap to resolve lights being on. This time, it’s not the gas cap. I have no pressure release when taking cap off. Help, please.. thank you in advance.
op2:
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