Toyota Repair Problems? Ask a Mechanic for Answers ASAP
HAs there ever been any other code set with the P0446 code? Do you have the definition of the code or do you need that too?
More specifically this code P0446 indicates there's a problem with the vent valve or CCV which stands for close canister valve. This is a control valve that is mounted on the left inner fender well near the brake master cylinder there is also a purge valve located there too. The reason why the 446 code sets is because it sees a leak detection when it runs a vapor pressure test and it controls that valve to close. Either the hoses are off or missing or the valve itself is not opening and closing. You can test the solenoid with battery voltage and ground to make sure clicks if you don't have an active testing scan tool otherwise it is difficult to accurately diagnose evaporative emission systems without a smoke machine and a pressure tester for the EVAP system.
If you live where heat is an issue it's possible could be a problem in the canister if all the hoses are intact and no cracks or leaks which normally would cause a P0 440 code to set along with the 446 code it is likely the close canister valve or CCV. It will allow air to pass through it only once opened or closed. You can apply voltage and make sure the seal inside the valve is working and in fact the valve itself is clicking. It's cheaper to just replace that versus paying someone to diagnose it. The canister is a lot more expensive. Unless you can find a dealer to do a correct evaporative emissions test to give you 100% diagnosis but is very difficult to find quality diagnosticians in the shop.
Sorry had to step away from my computer for a bit that is correct just replacing the bow may be cheaper than paying some diagnose this and could solve the problem. If you have not done so please do not forget to rate the information that I provided you at three or higher.