Hi guys my rig, 2002 sr5 4wd with 310k miles, has been throwing evap codes for a couple years now. Its been throwing the P0440, p0442 and P0446 codes. In June 2020 I attempted to fix it and replaced the roll over check valve and gasket along with the gas cap. That appeared to fix the p0442 code but the others still pop up.

In the mean time, I've put maybe 5000miles on it in the last 1.5yrs so it has not been a priority to fix it. I drove it the other day and noticed gas fumes near the rear of the vehicle so that reminded me I should take another look at it.

After doing a bunch of research, I decided to pull the charcoal canister out and inspect it for cracks or anything obvious. I did not find anything obvious. I pulled the O-rings out which were not cracked or hard. Greased them up and reinstalled. Inspected the rubber hoses and while they are old, they were not cracked or dry rotted. I plugged off the ports on the canister and it appeared the hold air. The vent valve actuated using a 9v battery and did open/close letting air flow.

So there was nothing obvious there. I check the voltage coming out of the connector under for the valve with the ignition on and it read 2.5v. That seems a little low to me but I also do not know what it is supposed to be. Can someone point me in the right direction here? I also checked the voltage at the purge valves under the hood, also showed ~2v on each of those.

I am open to suggestions. I do not have a smoke machine as of right now. That may change

You checked the vent hose running from evap to tank? Think there's one from tank to fill cap also. No drips when you fill your tank?

Read thru the FSM? It shows the 442 to be the same as 440, so the situation is standing still. More to test. See attached.

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Nothing obvious, I will check again. No drips that I can see.



Yeah I've been reading it. Will continue testing.

idiot alert.....and smoke machine for the win (also amazon, ordered smoke machine at 8:30 last night delivered at 11am). The vent line coming off the roll over valve was the issue. I didn't know there was an o-ring in there at the time and it looks like that didn't slide in all the way when I replaced the valve. Anyway, pulled the o-ring out to inspect, greased and re-install. now smoke is coming out where it is supposed to.

Another thing to remember is once codes are cleared, the monitor has to run again to complete the run cycle and OBD checks. You can get super geeky especially on the Mode 6 stuff, but Many times it requires a fuel level change of x% and so many mph for X distance to re run the monitor. EVAP systems are a pain. I think Toyota does it as good as anyone though. There’s way more older other brands with EVAP issues than Toyota in my experience.

I swear, people over filling damn gas tanks have killed more EVAPs, and worn spark plugs have killed more converters than anything else could ever kill cars……

Smoke machines are great. Definitely make short work of the task. What’s really nice is when you can actuate the solenoids through the ecm.

Got any recommendations? I was looking for something quickly yesterday but couldn't find much that wasn't full blown auto tech level and price. I would love something that is Laptop/Tablet/phone based and maybe for specific vehicles.

i found this, but its way more than I need: Launch Tech | Create Change

I run autoenginuity. There maybe something better these days though. That would let you do actuation on a lot of cars. I did run into my old 01 Subaru that it would not let you cycle the purge or the vent valves off or on it will. Come to find out Subarus protocol for Evap at that time frame was a bit stupid and really doesn’t work well. That wasn’t AutoEnginuity‘s fault, that was an ECM software issue.

I would start there, but there may be something absolutely better now. I’ve been waiting on them to release their iPhone wireless option, and they still haven’t yet.

If that’s the only thing you’re buying a scan tool to get fixed though, just take it to the shop. It’s not worth the investment for that alone. Take it from a guy that has spent too much money on tools over the years.

You should be able to do this with Techstream. Dongles on aliexpress are just a few buck, or under $100 for some of the "name brand" fakes that are supposedly plug n play. Or check out the links here https://www.toyota-4runner.org/3699126-post115.html

Bringing this back to the top. Looks like that vent line was part of the problem but not all of it. P0440 has returned, i don't drive the 4runner much so it takes a while for me to get results. However, every time I park after a drive, there is a strong odor of gas vapors that I can very easily smell. So I hooked up the smoke machine again and there is smoke coming out of the vent near the gas cap. I did confirm the gas cap is good.

Pulled the vent line at the charcoal canister and smoke is coming out of that vent when the engine and key is off. Is it supposed to be venting to atmosphere with the key off?

It is my opinion that there are things that are not worth fixing in a 20 year old truck, and the EVAP system is one of them. There are so many little hoses, metal tubes, valves, brittle plastic pieces. Too much to go wrong it just isn't worth your time chasing it.

While I agree with you, I live in CA and smog/registration is due...

Closing the loop on this. Finally passed smog today. Finally took it to a shop, they told me the charcoal canister was shot. Got an oem one on eBay for $400, installed it. Still had the problem. Got the smoke machine out again, finally found the gas cap leaking. Turn out the "new" gas cap I got sucked. Popped the one off my wife's 2015 4runner and what do you know it cleared up and the EVAP flags set within 5 miles of driving.....now it's got a new charcoal canister that I don't think I needed. Oh well.

Also, it turns out the EVAP codes weere masking the p0420 by not giving the computer enough time to actually throw the code. The 02 sensor is 2 yrs and 5k miles old so I assume it was good. Pulled, the cats and soaked them in some simple green purple industrial cleaner/degreaser. Put to all back together, cleaned the O2 sensor with some brake clean. It threw p0420 code in less than 10 miles. I either really killed the 310k mile cats or killed the O2 sensor. Got a new one, slapped it in. All readiness codes cleared and set within 10 miles of driving and off to smog we went! In the last 2 years I have put 4200 miles on this rig, 500 in the last 2 weeks troubleshooting but it's finally solved. Time for a detail and it's going up for sale

I have a 2002 sr5 4 runner. I have replace the Evap canisters under the truck and the Evap purger in the engine. It is still failing the emissions test. What else can it be?