Canister Purge Control Valve: Description and Operation

EVAP Vacuum Switch:

DESCRIPTION
The Evaporative Emissions (EVAP) Canister Purge Vacuum Switch is a normally open switch which closes when vacuum is applied. It is an input to the PCM to signal that the EVAP solenoid has opened, allowing manifold vacuum to draw fuel vapors from the charcoal canister into the intake manifold.