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Brad, ASE Certified Technician
Category: Buick
Satisfied Customers: 2366
Experience:  ASE Certified Master Technician. 15+ Years experience.
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2002 buick: the solenoid vent valve canister..gas cap..comes back

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I have a 2002 buick showing a PO446 code, i have replaced the purge vent valve on the motor and then the solenoid vent valve canister back by the tank and also a new gas cap. The code comes back in after about driving for 150 + miles. Could it be the charcoal cannister or the computer? I just failed my emissions inspection so i am in need of some ideas. Thanks
Hello and welcome to!

Make sure the vacuum hose going to the purge valve under the hood is intact, not collapsed, and provides plenty of vacuum to the valve.

Make sure the hose that connects the purge valve to the rear of the vehicle is connected at both ends and not damaged in between. Disconnect both ends and blow air through this line to make sure it isn't plugged up.

You very well could have a bad charcoal canister. Sometimes the charcoal in there comes looks and just plugs up the works. You can remove the canister and look for evidence of charcoal. Take the old vent and purge valves and lightly tap them down onto a piece of white paper. If you see a bunch of small black chunks come out that's a good sign that charcoal has contaminated the system.

Beyond this a leak in the system can set this code. Unfortunately leaks can be impossible to find without an evaporative emissions smoke machine and even then it can be very difficult to find.

And of course it could always be a computer but that would be extremely rare and there is no good way to test for this. Given the high price of a computer it's an expensive guess and usually only replaced as a last resort option.
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