Make sure the parking brake is applied.
The parking brake and brake system
indicator comes on for 15 seconds when
you pull up the electric parking brake
switch...
The system becomes ready to start searching for lane markings when all the
following conditions are met:
The vehicle is traveling between about 45 and 90 mph (72 and 145 km/h).
The vehicle is on a straight or slightly curved road.
The turn signals are off...