NHTSA, which announced the start of the probe in documents posted on a government website, said it was aware of six crashes in which six people were injured when airbags failed to deploy in frontal crashes, including four in 2011 Hyundai Sonatas and two in 2012 and 2013 Kia Fortes.
The issue in these vehicles are linked to electrical circuit shorts in the air bag control computers, which are developed by parts supplier ZF-TRW.
The crashes involve Hyundai Sonatas and Sonata hybrids made in 2011, and Kia Forte and Kia Forte Koups made in 2012 and 2013. Less than a month ago, Hyundai announced the recall of almost 155,000 2011 Hyundai Sonatas due to the risk that a short circuit could prevent the air bag deploying in the event of a crash.
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NHTSA says it's going to find out if other carmakers use similar air bag control units and whether they pose a safety risk.
"We are actively investigating what exactly causes the airbag control unit to become damaged in these specific types of accidents, but are announcing this recall now to ensure the safety of our customers", Hyundai said in a statement.
Hyundai spokesman Jim Trainor said the problem occurred in rare head-on collisions that were offset from the center of the vehicles. In addition, the agency will try to determine if other auto makers are using potentially faulty parts made by ZF-TRW. Kia said it will work closely with NHTSA on the investigation, "including monitoring and conducting additional crash testing as appropriate". Additionally, ODI is aware of a prior recall, 16V-688 where EOS appeared to be a root cause of air bag non-deployment in significant frontal crashes in certain Fiat Chrysler vehicles.