Faulty coolant control valve causing reduced engine power at highway speeds and reduced acceleration caused unsafe operation on highway. Was unable to safely maneuver to right lane on highway to allow faster traveling traffic to pass. Fortunately was only about 5 miles from home and was able to operate the vehicle in ‘limp’ mode after traffic cleared. There was no warning just during operation check engine light and reduced engine power displayed on the drivers information center. The vehicle is available for inspection with the defective part because GM can’t source a replacement despite occurring nearly eight weeks ago. GM has authorized the warranty repair and is currently at a Chevrolet franchise dealership awaiting repair parts. The manufacture is aware of the issue and has accepted a manufacture engine part is the cause of the issue.