A Loose or worn gas cap may cause Check Engine Light to illuminate.
Car Problem Reports
GMC Yukon Denali Check Engine Light Due to Gas Cap Issue
GMC Yukon Denali Problem
Visitor, 2007 GMC Yukon Denali
Got a diagnosis with a code using the code machine...the code could have been a couple things related to gas, but it was determined that it was just that the gas cap was too loose ....just replace the cap.