P0442 Fault Code, EVAP Smoke Test, and other questions

Hey Everyone,

I have a couple questions and seeking advice on EVAP small leak troubleshooting.

Symptoms: I got a check engine light, read it with an OBD scanner - confirmed P0442. I wasn't too surprised by this. I had been having a smell of gas coming from some where near the rear tank that could be smelled between the cab and bed as well as in the driver side rear wheel well.

Things I tried so far: My initial thought was bad gas cap seal, so I cleaned the mating surface of the gas cap on the filler neck, cleaned the cap itself, and cleared the code. No dice, It came back shortly thereafter. So I bought a new OEM gas cap. That didn't work either, code returned. I checked the EVAP VSV valve by disconnecting the hoses and attempting to blow through it unpowered and powered. Seems to be working correctly, not leaks could be felt. Next I bought a used DIY smoke machine and connected to the hose with the green service port. I saw smoke pouring out of the area around the gas cap (see grey arrows in photo). Since I had already replaced the cap, I assumed the filler neck was bad. So I replaced it with a new one and did the smoke test again. The smoke came out of the same spot. Examining the old filler, I now suspect that may be a vent of some sort.


My Questions:

• Does the filler neck have a vent to atmosphere that is normally open? My neck has four separate tubes and I suspect this one (red arrows) is a vent of some sort, it leads back to the canister (see red arrow in canister photo).
• I read the service port tag under the hood, it says to block the canister vent marked by a yellow line (see photo). I don't see that line, does anyone know which on is the vent? I suspect it may be that same line.
• Does anyone know what the other line on the filler neck are for? I suspect one is just to vent
• Does anyone have a manual for this system with schematics, troubleshooting procedures, etc...? Anything helps at this point

Appreciate your responses!

 

How much pressure are you applying through the evap port?

 

Approximately 1 psi

 

Please help cattywampus, I’m going thru the same thing, only I’ve changes the entire charcoal canister, purge valve under the hood, had it “smoke tested” by a shop, and put on an OEM gas cap, I’m suspecting it’s the breather house on the filler neck, may have gotten busted or cracked when the “shop” swapped out the charcoal canister. I’ll be keeping a close eye on this thread, as to not lose my mind and drink too much whiskey over it. Also emissions due in two months so I def need to finger this f****er out, thank you very much!!

 

May be time to drop the gas tank and inspect for corrosion at seals on panels at top of tank.
Or holes in tank.

 

Oof that sounds painful...

 

I forgot to mention I also did o2 sensor, in bank 2 if I’m not mistaken, I really do love this site. Thank you!

 

P0441 is for a small leak. Essentially the system has closed itself off after pulling a vacuum and measures pressure rise after a defined period. Depending on the pressure rise you either get a small leak or a large leak. During positive pressure testing via the evap port, you must block off the air drain hose. The charcoal canister has check valves that open during positive pressure to vent fuel vapor. This is used during fueling to allow vapor pressure to escape the tank, pass through the canister, then go to atmosphere. The confusing part to me on these trucks is that the air drain hose appears to route back to the fuel filter neck. My suspicion is that the gray piece on the fuel neck is separate from the fuel flow path. I would clamp off that hose near the charcoal canister and repeat the smoke test.

 

Oh! it would make sense why I got smoke pouring off the top of the filler neck. That must be a vent outlet that they moved there for some reason. So I probably prematurely replaced the filler neck, .

Okay, I'll try that and see how the test goes.

 

I meant p0442 above for small leak, not p0441. P0455 is large leak. Anyway, i think the smoke test is still the right way to find the problem.

The "yellow" line to be clamped appears to match the one that routes to the filler neck as well. See photos below:
https://twstatic.net/attachments/image-jpg.185020/
https://i.ebayimg.com/images/g/XYcAAOSwrLxak-gA/s-l300.jpg

 

Just throwing it out there, My 0442 and 0440 codes were both solved after replacing my fuel check valve. It had gone bad and the gasket around it was almost completely gone. If you haven't been able to pinpoint the issue in the easy to reach spots (fuel cap, under the hood, etc) I'd say it's time to either drop the tank or pull the bed to get a good look at everything.

My fuel pump took a dump, so I had no choice but to pull the bed and get it all changed. Personally, I think it's easier to pull the bed and go in from the top, since all the fuel lines and vac lines stay put and are easy to inspect. If you have an extra set of hands you can have the bed off fairly easily.

 

Found the leak! It was on the fuel pump tank seal (P/N 77169-04010) up top. Thanks everyone for the help. Special thanks to @tacoma4 and @Captain Magma for the help.

For anyone else reading this later who might be in the same spot: Clamp off that line in the red arrow (see my photos above). I also pulled off one of my smaller filler tubes that leads to the tank. I think this helped fill up the tank with nice thick smoke. Then when I reconnected that line I pulled off, the thick smoke starts to come out of the leak location and becomes more apparent. Hope that makes sense.

I also did not completely pull off the bed. I proped the front of the bed up in the front to gain room to see everything. I did this by taking out the front 4 bolts, and loosening up the rear bed nuts almost all the way. I used a jack to prop up the front of the bed and put blocking under it (see picture). I didn't have an extra hand to help me get the bed off else I would have done that.

 

Cattywampus, 2011 tacoma, replaced gas cap after code456- Evap small leak, after smoke test, smoke coming from around gas cap. I will tell technical to look at fuel pump seal. Hope this work. Thanks and God Bless