Products Liability Law Daily NHTSA to investigate airbag control units in 12.3M vehicles
Wednesday, April 24, 2019

NHTSA to investigate airbag control units in 12.3M vehicles

By Susan Engstrom

Approximately 12,300,000 model year 2010-2019 vehicles manufactured by FCA (Chrysler), Honda, Hyundai, Kia, Mitsubishi, and Toyota are equipped with an airbag control unit that could fail during a crash, resulting in non-deployment of the airbag and seat belt pretensioners.

The National Highway Traffic Safety Administration’s Office of Defects Investigation (ODI) has expanded the scope of an earlier airbag probe to include the tier-one supplier of the at-issue airbag control unit (ACU)—TRW Automotive Inc. (now ZF-TRW)—and any manufacturers that installed the ACU in their vehicles. ZF-TRW supplied ACUs to six automakers: FCA US LLC, American Honda Motor Co., Hyundai Motor America, Kia Motors America, Mitsubishi Motors North America, Inc., and Toyota Motor Corp. According to ODI, the ACUs may suffer electrical overstress due to harmful signals (electrical transients) produced by a crash event, causing the unit to stop working during the crash (NHTSA ODI InvestigationNo. EA 19-001, April 19, 2019).

Airbag control unit. ODI explained that the ACU senses a vehicle crash to determine whether airbag deployment is required and, if so, deploys the appropriate airbags and other supplemental restraints. Internal to the ACU is an electronic component (an application-specific integrated circuit, or ASIC) that monitors signals from crash sensors. A failure of the ASIC may prevent deployment of the required airbags and devices or may otherwise affect the proper operation of the ACU. The ACU is located in the passenger compartment, and electrical wiring connects the ASIC to sensors located at the front of the vehicle. ODI’s current understanding is that a crash event may, in and of itself, produce harmful signals on the sensor wiring capable of damaging the ASIC, although the probability of this occurring appears to be low. While the ACU incorporates electrical circuitry intended to protect the ASIC from harmful signals, the level and effectiveness of the protective circuitry varies by customer.

Preliminary investigation. During a "Preliminary Evaluation" opened by ODI last year [see Products Liability Law Daily’s March 19, 2018 analysis], Hyundai and Kia filed recalls (18V137 and 18V363, respectively) to address a defect that could result in ACU disablement and non-deployments. According to the filings, the disablement occurs in certain types of frontal crash events. Both filings discussed a condition known as electrical overstress (EOS) that affected the subject ASIC and likely was caused by electrical signals that entered the ACU via sensor wiring. The recalled vehicles used ACUs that had the lowest levels of ASIC protection, while non-recalled Hyundai and Kia products using subject ACUs had higher levels of protection. ODI has not identified any EOS failures in the non-recalled Kia and Hyundai populations.

Current probe. In September 2016, FCA filed a recall (16V668) for certain model year (MY) 2010 to 2014 Chrysler, Dodge, and Jeep products also manufactured with the subject ACU. In that filing, FCA also discussed an EOS condition that resulted in a failure of the subject ASIC, which caused airbag non-deployment. FCA noted that the defect condition had been observed only in vehicles equipped with sensor harnessing routed across the front of the vehicle. Other FCA vehicles that also used the subject ACU, but not the cross-car harnessing, had not experienced EOS failures, despite similar time in service. The recalled FCA vehicles used a mid-level form of ASIC protection. Other FCA vehicles that did not use cross-car wiring, or used higher levels of ASIC protection, have not been recalled. ODI has not identified any EOS failures in the non-recalled FCA population.

Recently, ODI has identified two substantial frontal crash events (one fatal) involving Toyota vehicles in which EOS is suspected as the likely cause of the non-deployments. The crashes involved a MY 2018 and a MY 2019 Corolla equipped with the subject ACU that incorporated higher levels of ASIC protection. Additionally, both ACUs were found to be non-communicative (meaning that the ACU could not be read with an event data recorder) after the crash, a condition found in other cases in which EOS occurred with other manufacturers. No other EOS events have been identified for other Toyota products (including Corolla models that used the subject ACU since MY 2011), or for the Honda and Mitsubishi vehicles that use the subject ACU.

ODI plans to evaluate the susceptibility of the subject ACU designs to electrical signals, as well as other vehicle factors that can either lead to, or reduce the likelihood of, an EOS event. Additionally, ODI will evaluate whether an unreasonable risk exists that requires further field action.

Among the vehicles included in the investigation are: Acura RLX (MY 2014-2019); Honda Accord (MY 2013-2015); Hyundai Sonata (MY 2013-2019); Jeep Wrangler (MY 2010-2018); Kia Optima (MY 2013-2019); Mitsubishi Lancer (MY 2013-2017); RAM 1500 (MY 2009-2012); and Toyota Corolla (MY 2011-2019).

Companies: Chrysler (FCA US LLC); Honda (American Honda Motor Co.); Hyundai Motor America; Kia Motors America; Mitsubishi Motors North America, Inc.; TRW Automotive Inc.; Toyota Motor Corp.

MainStory: TopStory NHTSANews MotorVehiclesNews MotorEquipmentNews

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