US Patent 9233666 Shift-by-wire vehicle and method to verify securement

A vehicle includes both a transmission park mechanism and an electronic parking brake. As a failure management strategy, a controller monitors vehicle movement to verify that the park mechanism is successfully restraining the vehicle against movement. Specifically, when the driver releases the brake pedal with the transmission park mechanism commanded to restrain the vehicle, the controller waits for a predetermined amount of time. If the vehicle moves during this time, the controller commands application of the electronic parking brake. The controller may also command application of the electronic parking brake if the vehicle does not come to a stop after the transmission park mechanism is commanded to restrain the vehicle.