Incident: Inadequately Soldered Transistors Cause Toyota Hybrid System Failure.

Published Date: 2011-06-30

Postmortem Analysis
Timeline 1. The software failure incident involving the recall of Toyota Highlander Hybrid and Lexus RX 400h vehicles from the 2006 and 2007 model years happened around mid-July 2011 as mentioned in Article [6112].
System 1. Intelligent Power Module on the control boards in some of the vehicles [6112]
Responsible Organization 1. Toyota Motor Corp. [6112]
Impacted Organization 1. Toyota Motor Corp. [6112]
Software Causes 1. The software causes of the failure incident were inadequately soldered transistors inside the Intelligent Power Module on the control boards in some of the vehicles, leading to overheating and potential loss of power or stalling [6112].
Non-software Causes 1. Inadequately soldered transistors inside the Intelligent Power Module on the control boards in some of the vehicles [6112].
Impacts 1. Loss of power or stalling of vehicles due to overheating transistors in the hybrid system's inverter, potentially leading to safety concerns and inconvenience for drivers [6112]. 2. Activation of warning lamps on the instrument panel and the vehicle entering a "fail-safe driving mode," allowing for limited driving distances before potential system failure [6112]. 3. Possibility of the power supply circuit fuse blowing, causing the hybrid system to stop and the vehicle to coast to a stop, posing a risk of sudden vehicle immobilization [6112].
Preventions 1. Implementing thorough quality control processes during the manufacturing of the vehicles to ensure proper soldering of the transistors inside the Intelligent Power Module on the control boards could have prevented the software failure incident [6112]. 2. Conducting rigorous testing and validation of the hybrid system's inverter components before mass production and release to the market could have identified the soldering inadequacies early on, preventing the issue from affecting a large number of vehicles [6112]. 3. Implementing proactive monitoring systems within the vehicles to detect early signs of overheating in the transistors or any other potential issues with the hybrid system could have provided warnings to drivers before the failure occurred, allowing for preventive maintenance actions to be taken [6112].
Fixes 1. The software failure incident in the Toyota Highlander Hybrid and Lexus RX 400h vehicles from the 2006 and 2007 model years could be fixed by replacing the inadequately soldered transistors inside the Intelligent Power Module on the control boards in the affected vehicles [6112].
References 1. Toyota Motor Corp. 2. Toyota website 3. Toyota Customer Experience Center 4. Lexus website 5. Lexus Customer Satisfaction

Software Taxonomy of Faults

Category Option Rationale
Recurring one_organization (a) The software failure incident related to the overheating transistors inside the hybrid system's inverter causing power loss or stalling has happened again within the same organization, Toyota. This incident led to the recall of about 45,500 Highlander Hybrid and 36,700 Lexus RX 400h vehicles from the 2006 and 2007 model years [6112]. The problem was attributed to inadequately soldered transistors inside the Intelligent Power Module on the control boards in some of the vehicles. (b) There is no information in the provided article about the software failure incident happening again at other organizations or with their products and services.
Phase (Design/Operation) design (a) The software failure incident in the article is related to the design phase. The issue was caused by certain transistors inside the Intelligent Power Module on the control boards in some vehicles being inadequately soldered during the manufacturing process. This design flaw led to the overheating of the transistor inside the hybrid system's inverter, resulting in the vehicles losing power or stalling completely [6112].
Boundary (Internal/External) within_system (a) within_system: The software failure incident in the Toyota vehicles was due to a transistor inside the hybrid system's inverter that could overheat because of inadequately soldered transistors inside the Intelligent Power Module on the control boards [6112]. This indicates that the failure originated from within the system itself.
Nature (Human/Non-human) non-human_actions (a) The software failure incident in the Toyota vehicles was due to non-human actions. Specifically, the issue was related to certain transistors inside the Intelligent Power Module on the control boards that were inadequately soldered, leading to overheating and potential power loss or stalling of the vehicles [6112]. This indicates a manufacturing or design flaw rather than a human error as the root cause of the software failure incident.
Dimension (Hardware/Software) hardware (a) The software failure incident in the article is related to hardware. Toyota announced a recall of certain vehicles due to a problem with a transistor inside the hybrid system's inverter that could overheat because the transistors were inadequately soldered. This hardware issue could lead to the vehicles losing power or stalling completely [6112].
Objective (Malicious/Non-malicious) non-malicious (a) The software failure incident described in the article is non-malicious. The issue with the vehicles losing power or stalling completely was attributed to a transistor inside the hybrid system's inverter that could overheat due to inadequately soldered transistors. This indicates a technical fault rather than any malicious intent to harm the system [6112].
Intent (Poor/Accidental Decisions) accidental_decisions (a) The software failure incident related to the recall of Toyota Highlander Hybrid and Lexus RX 400h vehicles from the 2006 and 2007 model years was not due to poor decisions but rather due to a technical issue with the transistors inside the Intelligent Power Module on the control boards. The problem was specifically identified as transistors that were inadequately soldered, leading to overheating and potential loss of power or stalling of the vehicles [6112].
Capability (Incompetence/Accidental) development_incompetence (a) The software failure incident in the article is related to development incompetence. Toyota announced a recall of vehicles due to a problem with certain transistors inside the Intelligent Power Module on the control boards that were inadequately soldered, leading to overheating and potential loss of power or stalling of the vehicles [6112]. This issue was a result of inadequate soldering during the manufacturing process, indicating a failure due to contributing factors introduced due to lack of professional competence in the production of the vehicles.
Duration temporary The software failure incident reported in Article 6112 regarding the Toyota Highlander Hybrid and Lexus RX 400h vehicles from the 2006 and 2007 model years was temporary. The vehicles could lose power or stall completely due to a transistor inside the hybrid system's inverter that could overheat. This issue was caused by certain transistors inside the Intelligent Power Module on the control boards being inadequately soldered. The vehicles would enter a "fail-safe driving mode" and could still be driven for short distances. In limited instances, the power supply circuit fuse could blow, causing the hybrid system to stop, and the vehicle would coast to a stop. Toyota announced a recall and mentioned that repairs would be done at Toyota dealerships free of charge once replacement parts were available, indicating a temporary nature of the software failure incident [6112].
Behaviour crash, omission, value (a) crash: The software failure incident in the Toyota vehicles involved a potential crash scenario where the vehicles could lose power or stall completely due to a transistor inside the hybrid system's inverter overheating. This would lead to the vehicle entering a "fail-safe driving mode" and potentially coasting to a stop [6112]. (b) omission: The software failure incident could also lead to an omission scenario where warning lamps would illuminate on the instrument panel, indicating a problem, and the vehicle would enter a "fail-safe driving mode." In limited instances, the power supply circuit fuse could blow, causing the hybrid system to stop, and the vehicle to coast to a stop [6112]. (d) value: The software failure incident could result in a value scenario where the system would perform its intended functions incorrectly due to inadequately soldered transistors inside the Intelligent Power Module on the control boards in some of the vehicles [6112].

IoT System Layer

Layer Option Rationale
Perception None None
Communication None None
Application None None

Other Details

Category Option Rationale
Consequence property, theoretical_consequence The consequence of the software failure incident described in the article is as follows: (d) property: People's material goods, money, or data was impacted due to the software failure. The software failure in the Toyota vehicles could lead to the vehicles losing power or stalling completely due to a transistor inside the hybrid system's inverter overheating. This issue could result in warning lamps illuminating on the instrument panel, the vehicle entering a "fail-safe driving mode," and in limited instances, the power supply circuit fuse blowing, causing the hybrid system to stop and the vehicle to coast to a stop. This directly impacts the property of the vehicle owners as their vehicles may experience these malfunctions, potentially leading to inconvenience and the need for repairs [6112].
Domain transportation (a) The software failure incident reported in Article 6112 is related to the transportation industry. Specifically, it affected Toyota vehicles, including the Highlander Hybrid and Lexus RX 400h, which are used for moving people and goods [6112].

Sources

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