2003 Yukon XL P0455 Evap Emission Control System Leak

I have a 2003 Yukon XL with the 5.3L engine. My check engine light came on. Checked codes and I have the following code: P0455 Evap Emission Control System Leak (Large). Any suggested culprits out there? Just looking for suggestions on what to check first, rather than the entire Evap system.

Thanks!

Never mind. Checked the obvious....Gas Cap was loose. Cleared code and code hasn't returned.