Fuel Evaporative System: Echo

EVAP system prevents fuel tank gasoline vapors from escaping into the atmosphere. Fuel tank gasoline vapors are routed through EVAP canister, then into air cleaner and intake manifold for combustion in the cylinders. Vapor pressure sensor and canister closed valve Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in EVAP system. See Figure. Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. Vapor pressure sensor may also be referred to as EVAP vapor pressure sensor. Canister closed valve VSV may also be referred to as EVAP Canister Closed Valve Vacuum Switching Valve (EVAP-CCVVSV). EVAP canister may also be referred to as charcoal canister. If a leak or an abnormality exists in EVAP system, a Diagnostic Trouble Code (DTC) will be stored in ECM. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article for retrieving of DTCs. EVAP Vacuum Switching Valve (VSV) is used to control EVAP system. ECM operates EVAP VSV which controls vacuum flow for EVAP operation. For EVAP system and component testing, see FUEL EVAPORATIVE SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS in appropriate SYSTEM & COMPONENT TESTING - 4-CYLINDER article.