The Forward Collision Alert seems to operate per the owner's manual description when the Adaptive Cruise Control is engaged, but does not operate when the Adaptive Cruise Control is NOT engaged. When engaged, the Adaptive Cruise Control slows the vehicle if the vehicle in front slows first. If another vehicle cuts in front of mine, the Forward Collision Alert green vehicle ahead indicator turns amber, the red flashing alert illuminates and the brakes are applied to slow the vehicle. When Adaptive Cruise Control is not engaged, the Forward Collision Alert green vehicle ahead indicator is illuminated but does NOT turn amber nor does the red flashing alert illuminate when a vehicle ahead slows too quickly or stops. I have been unable to find anywhere in the owner’s manual where it says the Forward Collision Alert only functions if the Adaptive Cruise Control is engaged. The manual implies these system should work regardless of the Adaptive Cruise Control being engaged or not. I reported this to the dealer service department. They hooked up their analyzer to the vehicle computer and said no fault codes were being displayed, therefore the vehicle must be operating as designed. I then wrote a letter to GMC Customer Support about this issue. After a few emails and phone calls, Customer Support referred me back to the dealer for resolution. This was useless as the dealer had already determined there was no problem. On November 10, 2016 a final phone call to GMC Customer support resulted in the following: 1. There was no one available at GMC Customer Support that could discuss this issue in technical terms. 2. If I was dissatisfied with the answer I am getting at the dealer, I could just go and take my vehicle to another dealer. This issue has been discussed at length on the Tahoeyukonforum.com website. Others have the same issue but no solutions. Either my vehicle is not operating as it should or the owner;s manual description of the system is inaccurate.