When does the canister vent valve close?

The canister vent valve typically closes when the vehicle's engine is running and the fuel system is pressurized, as part of the evaporative emissions control system. It also closes during specific driving conditions, such as when the vehicle is accelerating or decelerating, to prevent fuel vapors from escaping. Additionally, the valve may close during certain diagnostic tests conducted by the vehicle's onboard computer to monitor the system's integrity.