The canister control vauum check switch is installe din the vauum linke teween EVAP canister purge control solenois valve and EVAP canister purge controlv valve. (Built into EVAP canister) The switch detects vauum singal ot the EVAP cnister pruge control vavle, and send an ON of OFF singal to the ECM. When no vacuum is supllied ot the valve, the canister control vacuum check swithc send an ON singal tot eh ECM. When vacuum is supplied ot the valve, canister control vacuum check siwtch sends OFF signal to the ECM. The canister control vacuum check switch is not used to control the einge system. it is used only for onbarod diagnosis.