Canister Purge Solenoid: Description and Operation

Canister Vacuum Switching Valve:

The ECM controlled canister purge vacuum switching valve (VSV) is in the vacuum line to the purge control valve. Normally closed, the VSV opens when energized by the ECM. During idle or cold operation, the VSV is closed (de-energized), preventing canister purging. The ECM utilizes inputs from these sensors when calculating its control of the canister VSV:

Coolant temperature sensor
Distributor (crank angle)
Vehicle speed sensor