HI there
There are a few causes for this code. I would start by testing the vent control solenoid on the canister. If you remove it and then run power and ground to it, you should hear a clicking type sound. If it's good, then check for a plugged purge line from the canister to the engine.
P0446 PONTIAC - Evaporative Emission Vent System Performance Read more: https://www.autocodes.com/p0446_pontiac.html
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