Thermal Vacuum Valve - EVAP: Description and Operation

EVAP Vacuum Switch:

The EVAP Purge Vacuum Switch is used by the VCM to monitor EVAP canister purge solenoid operation and purge system integrity. The EVAP Purge Vacuum Switch should be closed to ground with no vacuum present (0% EVAP Purge Pulse Width Modulation (PWM). With EVAP Purge PWM at 25% or greater, the EVAP Purge Vacuum Switch should open.