FRONT COLLISION WARNING AND BRAKES DID NOT ENGAGE WHEN THIS SAFETY MECHANISM HAS BEEN FUNCTIONING IN THE PAST. WE WERE DRIVING ON THE FREEWAY IN TRAFFIC WHEN THE TRUCK AHEAD OF US BRAKED SUDDENLY. OUR PACIFICA REAR-ENDED THIS VEHICLE AT ABOUT 25-30MPH. NO AUDIBLE OR VISUAL FRONT COLLISION WARNING OCCURRED AND THE AUTOMATED EMERGENCY BRAKING SYSTEM DID NOT ENGAGE.