Toyota 77740-07020 Charcoal Canister Assembly

The fuel evaporative emissions control (EVAP) system absorbs fuel vapors and releases them into the engine intake during operation, where they mix with the incoming air-fuel mixture. The charcoal canister, located behind the fuel tank under the vehicle, stores fuel vapors when the engine is not running, transferring them from the fuel tank, throttle body, and intake manifold. When the engine operates, the purge control valve purges the vapors from the canister, allowing them to be consumed in the combustion process, with the electronic valve controlled by the PCM. A two-way valve on the fuel filler cap vents vapors to the atmosphere if the EVAP system fails, while a vapor pressure sensor detects abnormal pressure in the system, mounted in the fuel pump/sending unit assembly atop the fuel tank. Once the engine reaches a pre-set temperature, the Vacuum Switching Valve (VSV) opens, allowing intake manifold vacuum to draw vapors from the canister for combustion. The vapor pressure sensor monitors tank pressure and opens the VSV when a preset threshold is exceeded, admitting fuel tank vapors into the canister. To replace the charcoal canister, disconnect the cable from the negative battery terminal, raise the rear of the vehicle and support it securely on jackstands, unplug all electrical connectors, label and disconnect the vent hoses, remove the bolts, and separate the canister from the vehicle's underside, with installation being the reverse of removal.