Another EVAP thread: P0441 only (2004 DC)

So I got this truck over the summer and have been trying to get the CEL off since. I bought it with a P0453 code that would after a few days or weeks be accompanied by a P0451. Logic dictated that this was the vapor pressure sensor, which in the '04 is conveniently located on top of the damn gas tank. So that was fun. But at least I managed to turn those codes off. But now with a presumably working pressure sensor I am tripping P0441. This code is not accompanied by any others (like "gross leak" or "small leak") so I think that it is pretty cut and dry a bad purge valve?



What makes me scratch my head is the techstream data and if anyone could shine a light on what is going on here I'd be grateful:


To me it seems that (a) a GROSS LEAK test value could mean a leak just about anywhere. And (b) the -128.000 kpa test values showing PASS seem a little odd. Presumably the test value is the value the system got about pressure during the test. Am I getting that right? Which leads me also to (c) the fact that the difference between the GROSS LEAK threshold and my result is something like .04 psi. What kind of insane person created a system so sensitive to hang underneath a damn truck?

Some other info: I have no obviously rotted out hoses though a couple have small cracks forming on the inner walls when you look at the end that slips onto the plastic nipples in the system. Considering the low pressures the system runs at, I don't really think this should be an issue. I do on the other hand suspect my fuel filler neck has seen better days (yes, the gas cap has been replaced with genuine Toyota).

I'm gonna trust the diagnostic for now and throw a cheapie Amazon purge vsv on there. But I guess if that doesn't work then I need to do some smoke testing or replacing of rubber hoses next? Or just hang my head in shame and let the local mechanic figure it out in probably 45 minutes.

PS here's the truck:


It has been around the block but the important thing is that the frame was replaced under warranty 6ish years ago.

 

Kinda hoping this is my problem right there

https://vimeo.com/631306905

Is it supposed to be fluttering like that? When I apply 12v with leads it clicks and that’s that.

 

EVAP sucks. The sky-high view I'd share with most people going down this unfortunately shitty road is something like this:

In my experience, it's amost always a case of pressurization, either not enough or too much.

- If not enough pressure, chances are a line is loose/broken, charcoal canister is cracked, one of your purges is staying always-open due to failure or wiring.
- If too much pressure, purge valve is stuck closed or clogged, not releasing due to failure or wiring, or the charcoal canister is gummed up and needs replacement.
- It can also be neither, you may have a pressure sensor sending/reading bad, but you should be able to check your sensors are in-range with the tools you have.
- It can also be something as stupid as a gas cap, and I always, always recommend replacing with a genuine OEM gas cap before going any further on diagnostics.

Unfortunately, EVAP system starts at the tank and carries all the way up to the engine, so there's a lot of ground to cover. If you know someone who can smoke test for you, this is probably the fastest way to find an area to focus.

To me, the fun part is exactly what you're doing now: Looking at live sensor data to figure it out. I've tracked down issues on about half a dozen other brands over my life and hated every single one. The stupidest solution on all of them was a slowly dying fuel pump on a 94-98 era C1500. Again, shitty situation requiring dropping tank or lifting bed.

Anyway - good luck. Not sure if this info helps. Last thing you want to do is throw parts at the problem. Shit adds up fast.

 

Just watched video. Yeah. Valve may be stuck. Salt up there is harsh.

 

Thanks for the support! Yeah I replaced the gas cap prior to touching anything else. Also replaced the vapor pressure sensor to get from a double-whammy p0451/453 to this p0441.

Here is the vsv with 12v leads applied. Seems to click properly and I blew through it with my mouth to see if it was actually moving:

https://vimeo.com/631305014

I don't know if the vsv normally just opens or closes, or whether it operates in a slower or quicker frequency of clicks. Kind of finding both opinions online, though the manual is pretty clear that 441 alone means the valve is bad. If the fluttering isn't normal, then I guess it could also be wiring. God I hope it isn't wiring.

 

There's always an exception to the rule, but by all means, if it's cheap and available, replace it.

Several diag tools I've used on other vehicles will "flutter" the valve like in your 1st video, anywhere from 5-10 times. I'm sure there's a logical reason for toggling it that way.

If you're hearing clicks, it may be good? Maybe not? Have you looked up a price on the valve to see if it's a no-brainer to replace, like $15-30 range?

 

Yeah, I ordered a $30 version off Amazon. This fluttering goes on for a lot longer than 5-10 reps. Who knows, could be fine. I sure can't find anything else obviously wrong with various hoses though. A few that look like the below, but I bet that can hold the ~18 psi the system needs and I'm not getting a leak code.