That is similar to the EGR cleaning function procedure. Odd. That is also the same on Duramax. DM's had a bad issue with EGR's and carbon. As a bulletin I would update the software that would install a small extra program for EGR cleaning using a scan tool. Before you would have to remove/clean or remove/replace as a fix. Cost GM a buttload of coin under warranty. This fixed the problem. Anyways that is the sound it makes when you enter the cleaning mode using the scan tool