2003 Cadillac Escalade Esv emmission

Evap leaks can be kind of tricky. To assume that it may be the canister is probably false. To diagnose it, you either need a scan tool, or an evap tester that pressurizes the system with smoke, or both. Check your fuel cap, if it don't have a very positive ratcheting lock, it may not be getting tight enough. Possibilities include the vent solenoid, purge solenoid, fuel tank pressure sensor, fuel sender seal, hoses/tank/and connections, canister, filler neck, and cap. With a scan tool, you can possibly do a purge and seal function while watching the tank pressure data, perform some quick checks and monitor for improvements.