According to The Detroit News, NHTSA received 18 complaints about the brake pedal becoming hard to depress on these cars, increasing stopping distance. Drivers reported hearing a "pop noise or an air hissing noise when applying the brake pedal, followed by a hard pedal feel and reduced brake effectiveness," NHTSA told the News.
In a particularly terrifying incident, one driver says the Dart's braking system shut down while driving at 50 miles per hour. "I feared for my life. It is one of the scariest things I have ever dealt with," the complaint said, according to The Detroit News.
A Fiat-Chrysler spokesperson said the automaker is "fully cooperating" with this investigation.