rmk9785e

We're still getting the code, The technician has run tests and has indicated that he has not found any issues with the canister, various valves and hoses but there is still a leak somewhere. He is saying the next step is to take down the fuel tank to be able to reach the valves and components above the tank. This is a labor-intensive task for which he is estimating a cost of $500 plus any parts.
Does this sound right?

rmk9785e

My vehicle has had P0446 code for many months but now it is time for emissions test and I need to have it fixed.
Our tech who has worked for many years at a Toyota shop has run tests and has not found any issues with the canister, valves, and hoses but there is still a leak somewhere. He is saying the next steps is to remove the gas tank to reach and check out the valves and other components above the tank. My options are:
1- Let him take down the gas tank and continue with the diagnostics at a cost of $500+ parts which I can buy OEM from anywhere.
2- Take the car to a Toyota dealership that will charge me $250 for diagnostics which will be applied toward the repairs. Understandably, they are unable to estimate cost of the repairs (parts & labor) until having performed their diagnostics. Of course they will install their own parts which will be more expensive compared to open market OEM parts.
Please help me decide.

MattRX

Sounds like a smoke test needs to be done to pinpoint the exact area of the leak. There should be no need to remove the tank, just take out the driver side rear seat and remove the inspection cover and that should be sufficient enough to troubleshoot a leak, maybe combined with an inspection camera if space is tight.

salimshah

I too would advise you to take it to shop which has smoke machine to find leak(s). And if the location of the leak is above the tank, then ask the mechanic how he can reach/fix it. There are ways to cut a "U" shape on the floor and peel it back. If the tank needs to be dropped, then it needs to be dropped. Diagnostic [smoke] can be introduced from the engine bay. I am worst casing it as the leak maybe in the engine bay itself.

Salim

Arsenii

Hello,

Not really, P0446 usually indicates an Electrical malfunction, rather than Mechanical. Before dropping the tank, check that All the VSV solenoids in the EVAP system function as intended, especially the one on the Charcoal Canister itself, that's the one that caused this code for me back in the day.

Do not trust the fact that the VSV clicks or has continuity alone, that's how they get you. Mine had continuity, and did make some sort of click, but was rusted shut and jammed a bit, so it wouldn't fully open or close. To actually test it, connect it to a battery while blowing into one of the inlets, it is Normally Closed, so it should open when you power it.

Hope this helps and best of luck!

rmk9785e

Thank you. I'm questioning the relevant experience of this Toyota technician if he doesn't know that he could reach the components above the gas tank without having to take it down. I have spoken to a Toyota dealership that will charge me about $250 for diagnosis and will credit that amount toward repairs. Taking your advice, I am scheduling an appointment with them. I realize their OEM parts prices will be higher but I want to make sure it is done right.

rmk9785e

Thank you. My tech said he tested the valves by observing the clicks and continuity. I'm taking it to a Toyota shop.

hugo2648

Do some easy items first.

1. Clean the Fuel Tank filler area and tank cap thoroughly. Then apply grease to the O-Ring and the threads.
2. The charcoal canister has two larger diameter hoses going into it 5/8th I think). The dont have clamps. Install and tighten hose clamps to both ends of the hose.
3. Finally clean the MAF sensor just for kicks. I do not think that causes 0446

rmk9785e

Thank you all who have helped and guided my learning. Finally had to get it done at a dealership to pass inspection for registration renewal.
P0446 repair required 77740-48011 - Charcoal Canister assembly for $650.75 and $220 for labor.
The knock sensors replacement required a pair of 89615-32030 knock sensors at $252.37 each, 17177-20020 Intake manifold gasket at $56.55, 17178-20020 Intake manifold gasket at $54.84, 17176-62030 Air Surge Gasket, 82219-07010 Sensor wire at $91.26 and $680 in labor.
All in all, $2,213.36 (after discounts) for these repairs. I'm Ok with it since this car has 103,000 miles and has not had any major repairs since we bought it new in 1999.
I'm thinking of selling this car and replacing it with a more recent model.

Fit1too

Thanks for the follow-up. You know that thing will run for another 100K easily. I like the second gen, but not the cracked dash issue and oil line failures, and the newer models look odd.

hugo2648

My RX300 has 210K miles. These cars are bullet proof.

Arsenii

By sheer stroke of luck got myself P0446 again, along with P0441 a few days after my last post, following my own advice went to check all the solenoids first. I replaced the VSV near the Charcoal Canister at some point when said code showed up the first time, as it was jammed with rust and wouldn't function, had to retrofit a different style in there as the proper one cost way too much, here is a thread about it.

Since I already replaced the solenoid mentioned before not so long ago, I just checked that nothing came loose and went searching elsewhere. Next place to check was the Vent Solenoid under the hood, the one that allows vapor to enter the engine, and wouldn't you know it, the solenoid clicked when powered, but the valve wouldn't open when I blew into one of its ports, hence the code. The concerning part is that after I replaced the whole valve assembly, I figured I would check that Vent VSV again, and it ended up functioning normally. Armed with life lessons from the past about solenoids, I tried heating it for a good measure, and it still performed fine.

The reason why I am sure it was the Vent VSV under the hood is because it didn't function when I first checked it, and the code never showed up since I replaced the assembly, whereas before it will show right up in less than a day, here is a similar thread with the same outcome to mine, the person ended up replacing the whole Solenoid Assembly, any ideas are more than welcome. The point of this is to not trust anything, and if it is easy enough to replace, you may as well try it before tearing into the tank or dropping the rear subframe to access the Canister.

Hope this helps and best of luck!