EVAP Code: Charcoal Canister

Hello guys, happy new years.

I would like some advice on whether I am taking the right steps on fixing my issue with my 1st Gen Tundra 4.7 V8. My truck has these 5 codes: P043E, P043F, P2401, P2402, P2419. All EVAP Emission System Related. I bought the truck about 3-4 months ago and it’s been running with these codes, but I had to do emissions a few weeks ago and was unable to pass. I erased codes beforehand thinking it would pass but no look.

I’ve replaced with a new gas cap but that didn’t fix the issue. Not sure what else to do besides replacing the Charcoal Canister. Would this be a solution or is there anything else I should look for before replacing the canister?

 

Can you please be so kind and thoughtful as to give us your year of truck? That would be hugely helpful, since systems change across the years.

Replacing the charcoal canister is never the right move if that's not the source of your problem. The fact you have P2401 and P2402 which seem to be in conflict with one another (and indicative of wiring issue), I also don't think the charcoal canister is your problem.

Did you check the hoses attached to the canister? Are you hearing a pumping noise when the engine is running and hood is up?

 

Oops sorry.. it is a 2005.

I don’t hear a pumping noise, under the hood it sounds pretty smooth. I’ve done new valve covers, spark plugs, and a few other maintenance items and she runs fine. It idles very smooth too.

But.. I have not thoroughly checked the hoses near the canister. Should I look for a leak around the hoses?

 

And looking at the Toyota FSM for the '05-'06, it looks like there are only a few areas that can malfunction to cause that series of codes, I'm higlighting them here, diagnostics info on how to troubleshoot the problem are in section DI-891 of the Toyota FSM which is readily available.

These are the areas you need to look at per these 5:

• You have a hose or vent that's clogged and/or open
• The Vacuum pump is faulty (stuck off/on)
• Vent/puge valve is faulty (stuck open/closed)

 

Assuming you have a 2005-2006 here, but the purge/vent valve is here, check the hoses there - check the hoses to confirm they're OK and not blocked:

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Here's how to test the Purge/vent if you want to remove it:

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The vacuum pump itself is integrated into the canister as you may already know. Thsi diagram shows the vent/purge valve is (left pic), where the vacuum pump module is in relation to the canistor (right pic) is and a layout of the function of the EVAP system (bottom pic) - did you confirm the wiring to the canister/pump is OK and plugged in?:

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Some additional FSM troubleshooting that may be applicable/do-able w/o special tools:

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Hey Man, thanks so much for your help. I’ve looked through plenty of places for detailed help like that for my situation, but was unable to find any, but I guess I didn’t look hard enough.

I never troubleshooted those areas, so I will check those other areas, and hope that’s the solution. I will check back in if that fixes my issue, or if it continues. Cheers, and thanks again.

 

No problem, and FYI, you can readily download the FSM, it's posted all over the internet (one of many links).

I'd add, this is not a place I'd recommend using non-OEM parts, but ... Meh.

Also FYI, Toyota Maintenance channel on YouTube is great, he has this video that covers the canister and failures - this guy is a jewel, he really breaks things down super simple to help the layman understand.

https://www.youtube.com/watch?v=RBqjEklbVfs
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This video is for a 2003, but it may help at least visualize digging a bit deeper into things.

https://www.youtube.com/watch?v=Gh7VyyPUFKo​

 

Finally @48love this video breaks down locations of EVAP/emissions stuff pretty nicely on the V8:

https://www.youtube.com/watch?v=PT3fa-tutYU​

 

Thanks @shifty, very helpful information appreciate it very much!

 

@shifty` I think I'm close to cracking my EVAP issue. Gonna call you over to this thread where it is more appropriate.

I believe my vacuum pump isn't functioning (stuck off). When I run the Techstream EVAP test on my truck, there is no change in pressure/vacuum on step 2, which is where the vacuum pump is activated. See attached.



Thing is... I don't understand where the vacuum pump is.


Or, I dunno, maybe I do now. It seems that the vent valve (labeled detection pump above) also has a vacuum pump inside of it. Am I getting that right?

In which case, I guess I got a bad vent valve/detection pump combo 2 yrs ago when I replaced all this, but didn't know any better. I tested the vent valve and it works great both on the truck and on the bench. I had no idea that I was supposed to be looking for the functioning of a vacuum pump inside of this part too.

I'd love to take a look inside of this thing. Has anyone on the internet taken this one apart?

 

I think I saw a video of someone taking one of the valves apart and cleaning it out/futzing with it, but I think it was an earlier model that has the valve in the canister box below the MC/Booster, where it lives on the earlier vehicles. I’m not in a position to be able to hunt YouTube, but … I swear the video should be easy to find. I’ll see if I can find it. At least maybe you can use a 9v battery to figure out if the pump is actuating.

 

This video deals with replacement in the ‘03-04 like yours.

https://m.youtube.com/watch?v=1CTtChRKliY

 

Yeah, I can’t find the video. But it was for earlier year vehicles and it was more of a teardown video, showing a guy taking apart the motor out of the ‘00-02 trucks after removing it from the canister. So not directly applicable but at least it showed some basic diagnostics that should translate.

I bet you can use that one video to pull the pump and test it. Look at the wires; surely it only has two right? Power, ground?

 

Yep, I've done that... probably multiple times at this point. But only looking at the functioning of the vent valve. It does only have a + and - . The vent valve actuates perfectly on the bench and while attached to the car using techstream. But I had no idea there was a vacuum pump in there that was supposed to be doing something! I suppose I could test the vacuum pump functionality by covering the .02 in orifice and seeing if there is suction, or listening for the noise of a vacuum pump motor of some kind. But based on testing, it sure seems to be fried. I'd like to verify before I spent money, but I've also been looking for this issue for 2 years so I just went ahead and put an order in for a new valve at my local Autozone for $68. If it doesn't solve the issue, it definitely will be in returnable shape after I'm done with it. It is easily removed.

I'm assuming there is a pump like this in there and that it is dead:

https://youtu.be/kV3kGQ3eoOw?si=uIocAKME7mmtUiiK&t=278

Note that it makes a noise when it turns on. My "detection pump" is silent aside from the quiet motion of the vent valve.

 

More fun: my vent valve does not have a vacuum pump. I decided to do a deep dive into inspecting it before I ran over to the store. There's just no way there can be one inside.

I decided to look into a hunch at this point and pulled up a FSM for 2000-2003 trucks. All my confusion is a result of my truck being a 2004 Double Cab. But it has the 2000-2003 EVAP system, not the system in the 2004-2006 manual. Don't ask me how that works. I definitely have this setup:


Started doing the diagnostics from the 2000-2003 manual that I hadn't gotten to from the other FSMs I've read. Noted that my tank holds pressure very well, my VSV and EVAP Purge valve resistance tests well and they open and close as they should. Engine pulls vacuum through the hoses. Hoses have no leaks between EVAP purge valve and canister. Canister has no leaks.

One test has you pulling under 1 psi of vacuum from the diaphragm at the top of the charcoal canister toward the air inlet line. I didn't have a way to pull a vacuum at hand except with my mouth but I noticed that the diaphragm was basically not allowing air through. I hit it with a bit of compressor air and either broke it or fixed it, because it flows fairly freely now. I wonder if there was a charcoal pellet stuck in there. I didn't have time to run any tests but am curious about whether I actually found something wrong with my system. My goal is to see if I can find someone dissecting one of these now, which would give me an idea of what putting compressor air to it did.

 

So you do have the setup with a canister under the MC/booster? I wasn’t expecting that. I thought that ended in ‘03 or ‘04.

 

No, it is next to the gas tank and is almost exactly like the '04-'06 one, but it does not have a vacuum pump. I guess it is some weird hybrid? That diagram is from the 2000-2003 manual.

This is attached to my canister, just a valve and 2 electrical connector pins:


Instead of this thing with the metal band on it, which has a vacuum pump (and more electrical connector pins):

 

Still effing this chicken.

When the system is sealed with vacuum, what should the rate of vacuum decay be?

I see mechanic vids online saying the rate of decay is too fast on a car, but I don't have a sense of how long this system should take to leak its vacuum. It isn't completely sealed even with both valves closed (gas tank breather hose), so it has to decay at some rate. Depending on how fixed/broken my system has been in the past week, I've had it hold from 30 seconds to 3+ minutes (yeah, I may have busted the diaphragm on the charcoal canister with shop air ).

 

I'd check your lines and look for dry rotting.

On my old truck (not a Tundra) I had a series of Evap codes, in my case one of my evap lines was filled with charcoal. I would check for that 2nd, but look for dryrotted lines first.

 

The cannister contains a bag filled with tiny charcoal granules. If the bag deteriorates or ruptures, the granules get sucked into the lines and can clog the valve.

 

All lines have now been replaced, and I've smoked tested the system a few times. I've also pressure tested the canister and vent valve, vacuum/pressure tested the purge valve (could still be faulty if me testing with 12v power is different than the 5 or 9 or whatever pulse it gets from the ecu). It ain't leaking anywhere so far as I can see.

You know what... I think it is my vapor pressure sensor throwing the tests off. I noticed that my gauge pressure on the sensor (which does all the testing) always reads -10mmhg to start. Which I'm coming to realize doesn't make sense. Gauge is gauge, right? It should read 0 when equalized with the atmosphere?

 

Got an OEM pressure sensor and now my gauge pressure reads like .250 mmhg with the truck off, which is probably right (voltage reads dead on in the center of the recommended range per FSM). So the truck no longer thinks my purge valve is leaking.

I've driven it 3 or 4 times and the light has yet to come on, but the EVAP monitor has not completed and I saw a PENDING P0455 GROSS LEAK pop up the other day. I just took another test drive and got a PENDING P0442 SMALL LEAK. So I have two pending codes, monitor not complete and no MIL. Frustrating.

I've smoked the crap out of this system and the only place I get smoke is out of the filler neck vents. If/when the light turns on, I will smoke again and focus on the filler neck area.

One other thing I am trying is tightening my gas cap before and after every drive. I never bothered to have it click more than 3 or 4 times, but I noticed that if I give it like a good 360 degree turn or more, it gets tighter. There is also often a fuel smell when I am near that part of the truck, but since cranking it down I have not smelled it. And the small leak code appeared after I tried this strategy for the first time. So maybe cranking the cap turned my gross leak into a small leak? I dunno. The amount of effort it is taking to diagnose this instead of throwing parts at it is bonkers though.

And with a system that essentially works! In testing it hits maximum vacuum so quick with Techstream that I barely have time to stop it before the program shuts the purge valve down automatically.