The fuel evaporative emission control (EVAP) system absorbs fuel vapors and releases them into the intake manifold during engine operation, where they mix with the incoming air/fuel mixture. When the engine is off, gasoline in the fuel tank and residual fuel in other components warm up and evaporate, producing unburned hydrocarbon fuel vapors that would waste gas and pollute the air if released. In an EVAP system, these vapors are routed through hoses to a charcoal canister, which stores them until the vehicle operates again, thanks to activated charcoal that absorbs many times its mass in hydrocarbon vapors. The system includes the charcoal canister, canister closed valve, EVAP system Vacuum Switching Valve, vapor pressure sensor, air filter, and refueling valve, with most components located near the canister beneath the vehicle. The vapor pressure sensor monitors the pressure inside the fuel tank and, when it detects excessive pressure, commands the canister closed valve to open, allowing vapors to migrate to the charcoal canister while also routing fresh air into the tank to prevent a vacuum. When the engine runs under the right conditions, the PCM commands the purge valve to open, allowing intake vacuum to pull vapors from the canister into the manifold for combustion. The refueling valve controls vapor flow during fuel tank filling, while the PCM regularly checks for leaks by inducing a vacuum in the system. For component replacement, the EVAP canister purge valve is accessed by removing the engine cover, disconnecting the electrical connector and hoses, and removing the mounting bolt. The EVAP canister requires raising the vehicle, disconnecting electrical connectors and hoses, and removing mounting bolts, while the Canister Closed Valve involves disconnecting a vacuum hose and removing mounting bolts. The EVAP canister air filter, located near the canister, is replaced by disconnecting hoses and removing the retaining bolt. The vapor pressure sensor, found on top of the fuel tank, requires removing the rear seat and carpeting, disconnecting the electrical connector, and removing the retaining ring before replacing the O-ring and installing a new sensor.
Posted by ToyotaPartsDeal Specialist 
