The ECO light comes on when the vehicle is achieving fuel economy close to its rated performance.
Driving habits that improve fuel economy increases the time that the fuel economy light is on.
To enable or disable the fuel economy light, while in park, press the Vehicle Info button on the DIC until PRESS TO SET ECO is displayed. Then press the set/reset button to select off or on. For more information see Trip Odometer and DIC Operation and Displays.