In order to transmit power from the engine to auxiliary systems like the alternator and water pump, the 2015 Sierra belt connects pulleys on each of these systems with one on the engine. That means that these systems will stop working if the belt breaks, which could leave you stranded. Abrasions and cracked or damaged ribs are sure signs of a belt that's on the way out. Check out our selection of 2015 GMC Sierra serpentine belts to find the right part at the right price.