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 these vapors for combustion, 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. After the engine warms to a preset temperature, the vacuum switching valve opens, allowing intake manifold vacuum to draw vapors from the canister for combustion. The fuel tank vapor pressure sensor monitors pressure changes, opening a vacuum switching valve when a preset threshold is exceeded, allowing vapors into the canister. Some models feature multiple vacuum switching valves and a timer in the PCM to check for fuel vapor leakage after the vehicle is turned off. For replacement, disconnect the negative battery terminal, raise the rear of the vehicle securely on jackstands, unplug electrical connectors, label and disconnect vent hoses to the charcoal canister, remove bolts, and separate the canister from the vehicle, with installation being the reverse of removal.