I hope this proves helpful. My original codes were: P0441, P055, P056. (Before and after gas cap replacement.) But after squeezing the engine- side VSV tubing into it's fittings a week ago, my scanner showed ONLY P0456 ("small evap leak"). So maybe it's entirely an issue with the hose. Toyota did not put claps at either end of the engine-side hose into the VSV on the Gen4 V6 engines. This the VSV which is bolted on the engine, driver's side high up. (There's another VSV integrated into the evap canister above the spare tire. That canister and it's hose connections can generate the same codes, so see also: Code P0456 - When its not the gas cap).

Yesterday, I put in a new VSV, and I added clamps around the engine-side hose terminations. It's quite possible that I only needed the clamps - but I did the VSV as well. (Photo shows VSV and one clamp, after install.) After driving two 10-mile stop-and-go trips yesterday (0-50 MPH, a few stop lights), I left it overnight for the computers to execute the tests - and re-blow the failure code, if it was inclined to do that.

But today, it started clean. And after a couple of short trips, I have not seen CEL, or the associated dashboard errors lights. So: Maybe the second "repair attempt" after you see codes P0451 / P0455 / P0456, after a new gas cap, should be: put on the hose clamps which Toyota neglected to put on that dang hose.

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I mean it's possible, P0441, P0456, and P0455 are not limited to the Gas Cap; that's just a very likely candidate.

I also wouldn't entirely fault Toyota for that, you'd be surprised how a lot of those hoses tend to glue themselves onto their fittings naturally unless they're high-pressure so a clamp may not have been as important on that side of the VSV.

That being said, adding a clamp because 11yr old rubber hose is maybe not gripping as tightly as it should? Not gonna hurt anything.

Per my first post, the more serious leaks were resolved by adding clamps on hoses. But P0456 was thrown again, alone, and I proceeded into some more vacuum testing. (Got some cheap testing stuff from Amazon).

When I held the "main hose" from the gas tank (polypropene, about 1/2" diameter) into the canister really tight, the vacuum held a lot better. Two of these fat hoses attach to the canister, using identical and very weird connectors built into the hose ends. The proper fix for my bad connector would be dropping the gas tank and replacing the entire hose.

But unwilling to pay ~$250 for professional service, and unwilling to fight with all that weight myself, I have tried a 3-layer fix:

First, I slopped 3M boat sealant # 4200 all over the joint. To help it cure without exposure to air, I sprayed a light water mist from a spray bottle.

Then with the boat sealant still sticky, I wrapped it all with 181-B aluminum tape, 2" wide to minimize the number of possibly leaky edges. And finally, I wrapped the aluminum tape in another tape, a more durable and sticky automotive "heat shield" product, riding over all of the 181-B aluminum edges. So far, this is working well.

Conclusion? Suspect ALL hoses, not just the cracked rubber ones.

Thanks for the info Rick. Did you ever resolve this issue with the extra sealant around the hose? I'm trying to sort out a similar issue with my 2007 4Runner. Already replaced the gas cap twice (first was aftermarket, second was OEM). Still throwing the P0456 alone. Now on to more testing.

It hasn't been throwing the code since I smeared that stuff all over the joint bearing, and I pass DMV inspections. But it was a slightly messy and 'subtle' job, which has made me nervous about the problem coming back.

If it fails again, I'll let my Stealer-Ship replace the tube. (Dropping the gas tank isn't a "do-at-home" procedure for me, because it needs a full lift.) If ever disassembled, the 3M 4200 can be peeled off - and that's why I didn't use 5200, which would have made a permanent bond onto the canister lip.

I was wondering about the sealant permanence too. I'm not familiar with either of those types, but will keep in mind to use the 4200 if I have to go this route. Thanks.

Thanks for the info, my 2005 sport edition is giving me this code. Gas cap replacement did nothing. I will try clamps first.

After 9 months, it seems to be holding up quite well ... no more lit-up CEL, and no more code 456 occurrences.

Thank you for your post, it has given me some insight on what to try next...as I have replaced my gas cap already. I wonder if the cold weather change started this whole mess? Probably so. I will attempt the clamps and see if that helps. Thanks again!

For me, the clamps didn't solve the problem - it was the bad seal between the gas tank vapor pipe and carbon canister, at a failed O-ring joint. When I disconnected it and added a "smear" of that 3m "4200 boat sealant", along with exhaust-wrap mettalic tape - the problem was solved (permanently, AFAICT).

So, unless there is a visible problem with the friction fit hoses -you shouldn't expect that step to solve the problem. Still I agree with you to do that first - after 14 years, it certainly won't hurt anything, it might help, and it's only a 1-minute install.

WOW, NICE DIY fix

Road Trip and Similar Codes Appeared... I drove for over 2k miles and it is fine, but need to get home to check if this solves it. I bought a new gas cap on the trip, but that did not resolve the problem.

My Codes thrown were:
1/12: P0456, Evaporative Emission System Leak Detected (Very Small Leak), CONFIRMED
3/12: P0441, Evaporative Emission System Incorrect Purge Flow, PERMANENT
4/12: P0455, Evaporative Emission System Leak Detected (Gross Leak / No Flow), PERMANENT
7/12: P1603, Engine Stall History, CURRENT
8/12: P1604, Startability Malfunction, CURRENT
10/12: P1603, Engine Stall History, CURRENT
12/12: C1201, Engine Control System Malfunction, CURRENT


Hopefully claps do the trick.

Thanks for this post and I will follow up.

I was gonna do this cause I have those codes and found out I already had clamps on those lines. I guess in 05 they put clamps on it.

Thanks for the tips, but I added the hoses clamps and the Codes and Dash Lights came back on after about 20 miles.

Looks like I need to look at doing the last suggestion.