PO442, will NOT go away

I had a CEL driving me crazy on my '04 3.4L. Had the code for cats too, so 2 new cats, new SS muffler and pipes and new OEM gas cap. Code is gone for cats...but drove a mile down the road and CEL came back for PO442 "small EVAP leak. Back to the shop, smoke test entire EVAP/fuel system with no leaks..test valves with scanner, one is iffy, replace with new charcoal cannister. CEL goes away for a day and a half. CEL is PO442 AGAIN...pull bed, pull tank, pull fuel pump, smoke test all, replace all rubber lines and clamps, clean and reseal filler neck, put it all back together and....still have have the CEL and PO442 code!!!!! I've spent almost $3K and can't get rid of the friggin' light, what's my next move?

 

That's certainly a lot of effort and coin... I'm just going to ask, for the sake of asking, did you reset the ECU after any of the repair work? Or just clear the codes? If you didn't pull the battery cable it might be worth a shot. If you did, then... When you had the cats replaced, did you get new exhaust sensors? If so, what brand? From there you have to start looking up stream too. Intake, MAF, etc..

 

Cleaned the MAF, replaced air filter, Denso O2 sensors....I need to get this thing to pass emissions so I can renew the reg, I'm running out of time, money and patience

 

You mentioned the evap hoses but did you replace the rubber gaskets on the top side of the gas tank? My understanding is that when you start the truck it tries to pull a vacuum on the tank, if it detects a leak it will throw one of the evap codes depending on how big it thinks the leak is. I believe that's why some people are able to fix their evap codes by just changing the gas cap. I was fighting P0456 last year, eventually replaced the gas tank and all of the gaskets.



https://www.tacomaworld.com/media/albums/2020-12-gas-tank-decrustification.63925/

 

Totally understand... seems like my truck does that to me every 2 years... I know here in CA you can pay the reg fee without smogging it yet.. then once it's smogged your sticker will show up eventually.

 

Have you checked the gas cap? It sounds silly but it's worth replacing the gas cap if you haven't already. I think the rubber seals on those go bad pretty often, and it's only a few bucks to replace the whole cap.

 

Yup check all the gaskets on top of the tank. Mine was leaking there as well and I had a “very small evap leak code” which is even worse. I ended up pressurizing the fuel tank with about 5ish psi of air from the compressor and then spraying soapy water everywhere and eventually I found the leak at the gasket where the fuel sender mounts to the tank.

 

Did they replace the vent valve for the tank? Just replaced mine for that code and fixed it. It has a rubber seal as well, it’s a common issue for the valves to crack. You’ll smell gas in the fuel gas cap area when the truck is running. Smoke test didn’t show any leaks, I just watched YouTube vids and read a lot of forums to troubleshoot down to fuel tank vent valve, it’s cheap. Just need to drop the tank a little to get to it.

 

I'd replace EVAP canister it could have an internal leak...

 

Thinking out loud here… if the parameters for running the evap monitor test are never met the CEL will never come on. It all depends now on if the year of your truck allows a smog to be run with incomplete monitors. If it was me I would keep the fuel tank full, clear the codes and monitor the monitors.

 

what about the charcoal canister?

 

OP said he already replaced the charcoal canister

 

Interesting. I wonder if this will help with the famous p0440, p0441, and p0446 combo

 

Every, fucking, 3rd day! I just clear and drive on. No smog test in Michigan. I quit tossing parts at mine 3 years ago.

I swear, if someone figures out how to re flash the ECU on these '04 trucks, they will be set!

 

i just psy the guy at the shop $20 more to pass my thing. such a stupid thing to deal with

 

from the 2003 manual...

 

SO. being your in the salt belt.. i've had to replace a few tanks at work due to rust. a smoke test is hard to find the leak with when its small.. but im betting its either the top sending unit seal, or rust has gotten to the tank and created a pinhole leak.

 

I had an incident a couple of years ago in which the tank strap broke, causing the two vent lines along side the filler neck to disconnect. Took me a while to figure it out, which meant I had to live with a handful of EVAP codes until I did. Since then, I can smell gas whenever the tank is nearly full, but no codes. If I can smell gas, there must be a leak, so how come no code? Is it possible I inadvertently defeated some aspect of the EVAP system by accidentally connecting those vent hoses to the wrong positions (i.e., reversing them)? Seems unlikely.

 

When I was trouble shooting my "situation", I found this article to be a good resource: https://us.autologic.com/news/toyota-tacoma-evaporative-emission-faults. Make sure everything is routed correctly.