P0446 Code

Hello - Thanks for the info....... I show this code can be one of several things. Circuit Description Vapor pressure sensor, canister closed valve Vacuum Switching Valve (VSV) and pressure switching valve VSV are used to detect faults in EVAP system. DTC is set if EVAP system leak is detected or if there is a malfunction in EVAP VSV, vapor pressure sensor VSV or in vapor pressure sensor. Possible causes are: "¢ Damaged, disconnected or blocked vacuum hose(s). "¢ Fuel tank cap is installed incorrectly. "¢ Defective fuel tank cap. "¢ Vapor pressure sensor circuit is open or shorted. "¢ Defective vapor pressure sensor. "¢ EVAP VSV circuit is open or shorted. "¢ Defective EVAP VSV. "¢ Canister closed valve VSV circuit is open or shorted. "¢ Defective canister closed valve VSV. "¢ Pressure switching valve VSV circuit is open or shorted. "¢ Defective pressure switching valve VSV. "¢ Damaged fuel tank. "¢ Defective charcoal canister. "¢ Fuel tank overfill valve cracked or damaged. "¢ Defective ECM. Is the vehicle running rough, bad in any way or just threw the code? If it is running basically okay, then this is my suggestion especially since short of funds. Check all of the vacuum hoses really good. Especially the small ones and areas of sharp bends, sitting against something that could chafe etc, look at the area that it connects to for brittle and splits. I have attached 3 pic below to assist. Next, I would replace the fuel cap. Then clear the codes and drive it and see what you find.

It may be the canister etc.........but, when looking at the chart above I would start with the most probable and work my way down. Most of the time I have found either a defective hose or mostly the fuel cap.

Thanks for all the information and great diagrams. I forgot to mention that I had him replace the gas cap and I reset the code. It lasted about a week until the light came on again with the same code. The vehicle runs fine with the exception of the light staying on. I will look at the hoses( the pictures will be very helpful) next and report back.

Hello –

Thanks for the additional info…………..Lord willing it is something simple and you will spot it looking around, say a split hose etc.

Also, I am sure you did but want to make sure we are on the same page. We have see where how the gas cap connects, there isn’t a good seal. That is, rub your finger around the lip and threads for anything that may prevent a good seal. Some have been slightly bent, or nicked from the fuel hose being put in and prevented a proper seal of the cap.

Good luck and will be waiting to see what you found so the other reader and us too can gain the benefit.

Have a great Christmas if we don’t speak again.

I apologize for taking so long to get back to you, but I could not coordinate my schedule with my friend's to look at his car. On Sunday I was finally able to inspect all the hoses that you diagramed for me and all appeared to be in very good condition.
Please let me know what my next step should be. If I should replace the canister/valve, how difficult will it be to remove this from the vehicle.

Thank you!

Since ANY of the hoses, or valves in this sytem could be the problem, it would be wise to spend the extra money to test the system first! Mechanics use a smoke machine to pump 2psi of smoke into the system, where the smoke leaks out, the part is replaced. Throwing parts at it to try and help is a waste of your time, and friends money! Carefully check the gas fill tube, if the upper half is metal, look for pinhole rust on it...ANY hole, even a pinhole will set the code you have. EVAP VSV in engine compartment is more likley the cause than the canister.

If this problem is not corrected can it cause any damage to the engine. I am not experiencing any problems in engine performance at this time. I had the code cleared and currently waiting to see if it recurs. Thanks for your great advice.

This is a fuel vapor management problem(gas fumes), probably will not cause engine damage, unless too much fuel enters the catalytic converter, not likely.

[quote:c9bc9b9db0="merlin2021"]This is a fuel vapor management problem(gas fumes), probably will not cause engine damage, unless too much fuel enters the catalytic converter, not likely.[/quote:c9bc9b9db0]


The VSV is very problematic. I've seen two go bad on different cars in my family and a couple from work associates. Bad design and in fact the EPA sued Toyota to extend the warranty on this part.

Dear 2CarPros,

I realized that I never got a chance to update you regarding my wife's friend's Toyota. Long story short, I located a mechanic for him that would test the system at a reasonable cost and he never went. So, unfortunately I have no information regarding what part caused the code. As the saying goes, "no good deed goes unpunished"!
Thanks for all your information as I appreciated all your efforts.

Steve

You can lead a horse to water...
Your welcome!

Very true about Merlin's comment on the VSV.

My 2003 had a bad one that I changed, cost me $68 from Toyota.

On that diagram of the EVAP system under the hood, Canister Closed Valve VSV, what is the part number for it? What is the function of it? I thought there is a only purge solenoid (EVAP VSV on the diagram) under the hood.