To ensure that the driver refills the DEF tank, Duramax-equipped trucks will warn the driver when the fluid is down to a 1,000-mile range. A series of start-up warnings — including lights, chimes and messages — will become more frequent until the tank is empty. When the DEF fluid is down to a 100-mile range, the truck will be limited to only 55 mph. As the range declines, so will the vehicle's top speed. If the driver continues to operate the truck with a dry DEF tank, after a final warning and restart, the truck will operate in a “limp home” mode that limits speed to just 5 mph until the tank is refilled.