P0455 evap leak code problem tried everything nothing is working

I got the p0455 evap leak error on my 2003 tundra

I had the lines smoked and fixed
I changed the charcoal canister
I changed my fuel cap

what else could it be nothing has worked to fix this problem.

 

Where did they smoke? Only in the engine bay? p0455 is a gross (massive leak), so it should be obvious! If they smoked in the engine bay I suspect I know what they missed...

This thread is mandatory reading: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

The TSB section specifically:

• Cracked fuel filler neck TSB for 2003-2004 trucks. See here. Causes P0441, P0442, P0446 codes. But also check the 'RODENTS' section two bullet points down for another possible cause.
• ....
• RODENTS: Lots of plastics, wire sheaths, etc. in these trucks use soy-based plastics. If you have rodents nearby, or you park outdoors regularly, it's not uncommon for them to crawl in the opening under the intake manifold, where the starter & knock sensors live, and chew up the wiring (no start, knock sensor circuit codes). Likewise, they love nesting on top of the gas tank, and they'll chew up both the wiring like this, killing the pump (no start), and chewing up the tank tubes/plastics like this (EVAP codes, EVAP small leak, EVAP large leak). They'll chew through the gas filler neck, which will also throw EVAP codes, like this. It's common enough we can share exact photos of it, and there are more where those came from.

 

Mother fuckin’ soy…..

 

Well today I checked for a Cracked fuel filler neck TSB and I did not notice anything cracked.
The mechanic smoked the lines for the evap system and fixed a leak he found in one of the lines but did not find anything else!

I am clueless of what I should do now. I've checked everything and nothing seems wrong but I still get the code

 

The cracks aren't always obvious in the filler neck. I don't think simply looking at it is going to answer that for you. You'd need to check while it's being smoke tested. Is your truck in the "affected VIN" list, or not? If not, probably not what's up.

Maybe it'll help to understand the EVAP system. EVAP is the SEALED (or at least controlled) system of fuel/vapor delivery from the gast tank to the fuel rail. Your vehicle is plumbed from the tank, up to the fuel rail, and back to the tank again. Part of that system is liquid plumbing, part of it is air plumbing for vapor control. There's also a vent/puge valve on that system of air/fuel plumbing which your on-board computer ("ECM") controls, the computer can open/close that valve to make the amount of vacuum in that plumbing optimal for fuel consumption.

The ECM has sensors to monitor the pressure/vacuum in the overall system, which is how it knows if/when to open the vent/purge valve. The computer also knows if/when the valve is open/closed - it can monitor the valve and will throw a separate code if it's stuck closed, i.e. vacuum pressure too high, or if stuck closed, throw a code pressure is too low). If it knows the valve is closed, it expects to hold a specific pressure, with the vacuum that's created as it sucks and returns gas to the tank, and natural other influences. If the vacuum is slighltly low, like a vacuum hose is cracked, it may throw a P0456 code. If a vacuum hose is totally comprimised/separated/unseated, it'll detect a larger leak and throw P0455. If that's the only code thrown, and you don't have another code with it to indicate, say, the vent/purge valve is stuck open, then you're looking for some other massive seal breach.

Obviously, maintaining vacuum in the system is interesting b/c one side of the plumbing has a huge ass hole in it: The gas filler neck. That's why auto manufacturers design the gas cap as a valve also. It's why you MUST turn your gas cap until it clicks after filling up, so you have confirmation of it sealing. The gas cap has a valve inside the cap itself, which can fail also. This is why, when you get minor leak codes, like P0456 specifically, people will say, "replace your gas cap". Sometimes aftermarket gas caps, locking ones especially IME, will throw this code because they suck.

"Gross" leak is pretty significant. We're talking, a significant hole, like:

• Vent/vacuum hose is totally unplugged somewhere in the system
• Charcoal canister between your brake booster and battery (on earlier-year trucks) has a major crack or hole in it
• Rodent chewed on plastics at the gas tank or filler neck -> It has happened a lot, check that "mandatory reading" thread I linked above for squirrel chewing on filler neck AND rats chewing gas tank plastics
• Filler neck is cracked along a seam of some sort

In any of these cases, since the system is sealed, pushing smoke into the system should reveal the source of the leak, it should be obvious where the smoke is coming out. But, in the case of say, rodents chewing on plastics on top of the tank OR the fuel filler neck, your mechanic is probably going to have their head up in the engine bay looking for the leak and may neglect everything happening on the lines as they travel past the firewall.

If I'm telling you shit you already know, it's not my intent. I type fast, and knowing this info is basically what helps "aha!" moments happen for others. If you didn't know this stuff before, now you know what to look for.

Is it possible your mechanic fixed the issue? You'll never know until you either (A) complete a drive/readiness cycle so the ECM realizes there's no longer an issue or (B) clear the codes and drive around to complete the readiness cycle.

Generally speaking, the rubber hoses used in vehicles are rubber, they decay. A lot of times the hoses crack and split at the ends, and it's really obvious. Sometimes simply trimming the last 1/2" off and re-seating them will solve minor leaks, but at the point the ends are cracking, you should replace.

 

I know this is gonna sound crazy! But my P0455 code that could not be found, did not show any leaks from a smoke test, and had every single possible part replaced including vacuum lines... get ready.. was caused by master cylinder leaking into the vacuum assisted brake booster which, because the vacuum came off the engine, sucked brake fluid into the intake. The brake fluid is not combustible so it doesn't burn off. My computer was assuming the fluid in the intake was gas unburned because not enough air to ignite all the fuel which would have to be because of a gross leak. The code popped up a year and a half before I lost the ability to stop my truck. Spent almost another year chasing the leak. Decided that just maybe... I pulled the vacuum line loose from the rear of the intake where no fuel or liquid of any kind should be and guess what.... Line had fluid in it still. I connected a vacuum pump with a fitting turned on the vacuum and pitch black zero viscosity brake water sucked up into the vacuum. Turns out it would boil rise to the top in the form of steam then condense and fall right back down. It had no way to burn off and no way out. I left it open for a week and a half borrowed my brothers truck and loooong story short ... I don't have P0455 code any more.

 

Appreciate this, interesting avenue to check because we’ve seen plenty of cases where the booster is accumulating brake fluid outta the MC. Technically the check valve on the booster (the plastic part the rubber vacuum line attaches to) is supposed to be one-way, allowing vacuum to enter, but not exit (IIRC). So it sounds like your problem was two-fold: You have fluid accumulation and the booster check valve failed.

Curious, what year/engine is your Tundra?