The invention controls a power cinching function of a motor vehicle door latch in order to improve door seal performance under conditions wherein vibrations could otherwise reduce seal effectiveness. With the door latched closed in a flush condition, the vehicle speed is compared to a slow-speed threshold. When the vehicle speed is greater than the slow-speed threshold, then a vehicle vibration parameter is compared to a vibration threshold. When the vibration parameter is greater than the vibration threshold, then the power cinching function is activated to move the door to to a subflush condition which increases a compression of the seal between the door and a vehicle door frame. When the door is in the subflush condition, the vehicle speed continues to be compared to the slow-speed threshold, and when the vehicle speed is less than the slow-speed threshold then the door is released back to the flush condition.