Toyota recalls hybrids with defective inverters


Torrance, Calif. – Nov. 7, 2017 – Toyota Motor Engineering and Manufacturing has recalled a handful of hybrid vehicles with defective inverter assemblies, according to documentation submitted to the National Highway Transportation Safety Administration. The campaign affects 2016 Toyota Prius hybrid sedans produced between Dec. 15, 2015 and June 8, 2016. Toyota is unsure how many of the recalled models contain defective parts.

The Defect

The vehicles referenced in the action come equipped with inverter assemblies whose capacitors may not be properly secured to the inverter housing. This assembly flaw leaves the capacitor terminal vulnerable to damaging vibration during vehicle operation, increasing the likelihood of a complete hybrid system shutdown. In the event that this occurs, the vehicle loses all motive power, creating a serious safety hazard for occupants. While capacitor terminal damage results in engine shutdown, the power steering and braking systems continue to function normally.

Toyota has yet to receive field reports detailing any accidents or injuries.

Timeline of Events

In April 2017, the automaker received a report from a U.S. dealer detailing an instance in which a 2016 Prius failed to failed to start, according to an internal document submitted to the NHTSA. Toyota engineers recovered and inspected the inverter assembly in the vehicle, and found that capacitor mounting bolts were missing. They also discovered that the capacitor itself had incurred terminal damage. The car company launched an investigation to determine how the capacitor bolts had gone missing, focusing on production data and records of the inverter installation process. Toyota found that the inverter assembly had been reworked during capacitor installation and that personnel had failed to re-install the bolts. Toyota soon amended its capacitor installation workflow to prevent similar scenarios from unfolding in the future.

In July 2017, engineers at the vehicle manufacturing company initiated replication tests to better understand the capacitor terminal damage observed in the vehicle in the report. Staff simulated operational vehicle vibration and applied it to the inverter assembly with the unbolted capacitor. Toyota found that the capacitor was prone to damage in these conditions. It initiated bench testing in an attempt to replicate the engine failure mentioned in the report, but was unable to do so.

One month later, Toyota received a report from the European market outlining events similar to those detailed in the April report from the U.S. market. Toyota recovered the inverter assembly from the vehicle referenced in the report and found that capacitor mounting bolts were missing. The capacitor terminal had sustained significant damage. Resin from another nearby part also melted within the inverter housing. Toyota installed the inverter assembly in a trial vehicle to see if the component, when stressed, led to complete engine shutdown. During the subsequent test, the trial vehicle lost all motive power, as the hybrid system ceased operation. The car company disassembled the inverter assembly used in the trial car and found that the capacitor terminal had sustained further damage.

With these results in hand, Toyota officials concluded that vehicles with inverter assemblies that lack capacitor mounting bolts are vulnerable to complete engine shutdown. On Oct. 12, the car company chose to conduct a voluntary safety recall. As of that date, Toyota had received one warranty claim and zero technical field reports related to the defect from dealers in the U.S. market. Dealers received notification Oct. 18.

The Solution

Toyota has instructed dealers to replace the inverter assemblies in affected vehicles free of charge, according to an NHTSA recall acknowledgment document. The organization plans to notify owners via telephone in December. Those in need of more immediate assistance can connect with Toyota customer service staff at (800) 331-4331. Callers should use the internal recall identification code H0U. Owners can also reach out the NHTSA directly using its toll-free Vehicle Safety Hotline at (888) 327-4236.

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