2008 - P0446 Evaporative Emission Control System Vent Control

Likely not the case but mine had both a leaky fuel line and a hole in the vent line from the tank to the canister .

usually have to find the leak

 

In my sienna which is a Toyota van there's a vent valve or vacuum switching valve back near my gas tank that goes bad and is a known issue in this vehicle our Prius may have the same I don't know where is it where it is but it would be a VSV possibly in the rear of the car for the evap system I'm not where I can look at a schematic right now.

 

Evap system faults can be tough to figure out- for anyone. Most of the parts are located on top of the fuel tank, and access is bad. Really all you can do is try to perform the bidirectional tests to check function of the purge solenoid valve (on the engine near the water pump belt), the bypass solenoid valve (located on the evap canister on top of the rear of the fuel tank) and the leak detection pump (located on top of the right front corner of the fuel tank). Trigger each test and try to listen for (or feel if you can put fingers on each part) the part clicking when commanded on.

I don't remember if a Gen2 will let you monitor what each step does during the automated Evap system function test. If it does then that should give you data to see what part fails.

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Welcome back to PriusChat!!

Here is the workup for DTC P0446 (and P0441) : https://attachments.priuschat.com/attachment-files/2019/07/170016_cip0441.pdf

Use techstream to run the evap tests, and post the results here.

This thread should get everyone up to speed : P0446, Techstream TBP Fail, and CCV Replacement | PriusChat