Q: What is the purpose and operation of the Evaporative Emission Control System and Vapor Canister?A: The Evaporative Emission Control System stops gasoline vapor escape by providing a sealed fuel system that keeps and condenses these vapors. This system includes a carbon-filled canister for vapor absorption, a vent cap, and a purge valve. The PCM controls the vacuum to the canister based on the engine. The fuel tank is sealed with a pressure-vacuum filler cap.