Ok so our 07 Denali has been running just fine with no codes since the dealer replaced the Trans Internal Mode switch... until the CEL came on with a code of P0449. No other codes.. I understand its the Evap Control circuit stuck in an "open" state. The problem im having is that I dont have any visual reference to know what is in this circuit or where the components are located so i can start troubleshooting. Anyone have experience with this code and components?