Airbags are supposed to keep drivers and passengers safe. But what happens if the airbag control unit (ACU) is defective? Will anyone know it’s defective until an accident actually occurs? And what if the seatbelt tensioners are also involved? The complaint for this class action alleges that ZF TRW Automotive Holdings Corp. sold faulty ACUs, and that Hyundai Motor America, Inc. and Kia Motor America, Inc. kept putting them in cars and downplayed the serious risks involved, even though they knew better.