Here is a diagram showing the location of the canister ahead of the right rear wheel well under the vehicle.
The purge valve on most vehicles is under the hood. Purge opens when the vehicle is running under certain driving conditions to burn the stored vapors from the canister. Its usual position is closed.
If this valve fails to seal it will set a code for a leak failure. These valves are usually not the ones that fail the most.
The shut off valve on the other hand is normally open and closes only when the system runs a test to check the integrity of the system.
If this valve sticks closed it makes it hard to fill the fuel tank. Or if it sticks open the test will fail because it leaks.
Because they are more exposed to road debris and damage they are usually the ones that fail.
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