Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
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the only way to know for sure is using a smoke machine to check for leaks and to energize the solenoids manually or with a compatible scan tool
a compatible scan tool is also required to check the fuel tank pressure sensor.
This type of diagnostic with smoke machine and compatible scan tool runs 100 dollars at a shop.
I can tell you the Evap canister vent valve is by far the most common failure that cause p0446
so if I had to make my best guess without using the diagnostic equipment I would suspect the canister vent valve
click here to view location of the canister vent valve
click here for further information on testing for p0446
special tools are needed to diagnose it properly (smoke machine/compatible scan tool)
but as I mentioned I would suspect the Canister Vent Valve
let me know if you need more help