The issue is with the vacuum pump, which can diminish vacuum over time, affecting braking and "extending the distance required to stop the vehicle, thereby increasing the risk of a crash," according to a letter to GM from the National Highway Traffic Safety Administration.
GM will notify owners of the issue, NHTSA said in the letter, which was dated September 10 and available Wednesday on the agency's website. The issue affects nearly 3.5 million pickup trucks and sport utility vehicles, including the Chevrolet Silverado (2014-2018), the GMC Sierra (2014-2018), the Chevrolet Suburban (2015-2018) and the Cadillac Escalade (2015-2017).