Anyone know what condition triggers the ECM to close the vacuum switching valve for the closed canister valve? I have a 2000 Camry, 4 cyl and I am getting a humming noise from the air inlet valve on the charcoal canister when the canister is being purged (the EVAP VSV opens to the intake vacuum). When I plug the air inlet line to simulate the CCV VSV closing, the noise goes away. Also, the CCV VSV does close when I put battery voltage to it. I am getting DTCs of P0440, P0441 and P0446 and all components worked and met specs when I did the TSB diagnostics. Any thoughts? Thanks for reading.