* Gas Tank: This is the starting point. The EVAP system controls vapor from the fuel tank.
* Canister: This charcoal canister absorbs fuel vapors. It's typically located under the vehicle, often near the rear of the fuel tank or along the frame rail. Its exact location varies slightly depending on the specific truck model.
* Purge Valve: This valve controls the release of trapped fuel vapors from the canister into the engine to be burned. It's usually located near the engine, often in the engine bay, connected to the intake manifold or throttle body.
* Vapor Lines/Hoses: These lines connect all the components together. They run throughout the undercarriage and engine bay.
* Sensors: Various pressure and temperature sensors monitor the system's operation. Their locations vary but are usually close to the components they monitor (e.g., a pressure sensor near the gas tank or canister).
To find the specific location of each component on *your* 2003 GM truck, you'll need to consult a repair manual specific to your truck's make, model, and engine. A Haynes or Chilton repair manual, or a digital version from a site like AllDataDIY, will provide diagrams and precise locations. You can also use online resources by searching for "[Your Truck Year, Make, Model] EVAP system diagram".
Remember to be careful when working under the vehicle; properly support it on jack stands. Also be aware of fuel system components – avoid sparks or open flames.
