where is the evap switch located on 2004 GMC Yukon XL Denali

i was told that there is a problem with my evap switch on box or box i would like to know where this is located thanks for any help.

Asked by for the 2004 GMC Yukon XL Denali
The evap system does not us any "switch" that I know of. The evap components are: Canister, Purge Solenoid, Vent Solenoid, and Fuel Tank Pressure Sensor. If you can provide the fault code that triggered the diagnoses of a faulty "switch" perhaps I can help you.
p0446 evap vent circ. is the code that I was given

1 more answer
The evaporative control (EVAP) system captures any raw fuel evaporating from the fuel storage system (e.g. the fuel tank, filler neck, and fuel cap). Under precise operating conditions dictated by engine temperature, speed, and load, the EVAP system purges these captured fuel vapors back into the combustion process.

and if you can provide the code, may be I can help you.