Laguna Hills, CA – October 15, 2018 – Toyota Motor Engineering & Manufacturing (Toyota) is recalling certain 2010-2014 Toyota Prius and 2012-2014 Toyota Prius V vehicles due to excessive voltage in the inverter which may cause the hybrid system to shut down and the vehicle to stall while being driven. This recall affected more than 80,000 vehicles, including ones subject to prior recalls.
The Defect
According to the NHTSA Recall Safety Report, the vehicles subject to this recall contain software used to control the Intelligent Power Module (IPM) within the inverter assembly. This module is part of the vehicle’s hybrid system. Certain characteristics of the software used to control the boost converter in the IPM could cause higher thermal stress than normal to occur in specific transistors in the IPM, specifically during high-load driving activities, such as accelerating during highway driving. Over time, stress could damage certain transistors.
In limited instances, the motor/generator ECU could reset, or – if a specific transistor within the IPM fails in a certain way during a high-load driving condition – an abnormally high voltage could be generated. In either case, there is the possibility that the hybrid system could shut down instead of entering a failsafe driving mode, which could cause the vehicle to lose motive power while driving at higher speeds, increasing the risk of a crash. Drivers may be warned of transistor damage via the illumination of various warning lights and the display of a warning message on the instrument panel.
Timeline of Events
Between the month of January and March 2018, based on VOQs and other available information, NHTSA contacted Toyota about allegations of potential incidents where vehicles experienced a loss of motive power while driving at some time after having received the software updates from prior, related recalls (14V-053 and 15V-449.) Toyota began reviewing the information and recovering parts from the field.
Toyota conducted a search of available data for vehicles involved in 14V-053 and 15V-449 and identified a limited number of instances where the data in connection with certain inverter-related trouble codes suggested a possible “ready off.” Based on an initial analysis of recovered failed parts, damage was observed in certain transistors. Toyota surveyed vehicles to identify the software version present in field vehicles, and, in those cases where an inverter failure occurred. Continued analysis of the recovered failed inverters and freeze frame data in a limited number of cases did identify an unexpected, abnormally high voltage value related to the hybrid boost converter.
In September 2018, a design review of the software used to control the hybrid system components in addition to a review of the inverter circuit design identified a potential mechanism for the hybrid system to shutdown instead of entering a failsafe mode based on the observation of an abnormally high voltage in extremely rare cases. Toyota could not exclude the possibility that a limited population of vehicles did not successfully receive a software update in one or both of the ECUs, and the company decided to conduct a voluntary safety recall campaign.
The Solution
According to the Toyota Defect Information Report, Toyota will notify owners, and dealers will update the software for the motor/generator control electronic control unit (ECU) and the hybrid control ECU as necessary, free of charge. Interim notices informing owners of the safety risk began October 22, 2018. Owners will receive a second notice when the remedy becomes available.
Owners may contact Toyota customer service at 1-888-270-9371. Toyota’s number for this recall is J0V. Owners may also call the National Highway Traffic Safety Administration Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153). The NHTSA Campaign Number for this recall is 18V-684. The software updates in this recall are needed even if the vehicle had the software previously updated under recalls 14V-053 or 15V-449.
