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Toyota Unintended Acceleration: It Wasn’t Just the Floor Mats

toyotawreck(Photo from “Oklahoma Jury Finds Toyota Liable For Sudden Acceleration Fault; Awards $3M In Damages,” by Arjun Kashyap, 25 Oct 2013)

Back in 2009 this newsletter started to express skepticism about Toyota’s insistence that unintended acceleration in their vehicles — in some cases resulting in fatalities — was due to a floor mat that could cause the accelerator pedal to stick. (Those earlier posts are listed at the bottom of this post.)

The reasons for the skepticism were (a) the number of reported cases was relatively high compared to other non-Toyota models, (b) there was at least one case where it was clear that a stuck pedal could not be the cause, and (c) the investigation by the National Highway Traffic Safety Administration (NHTSA) appeared to have some major flaws. Also, DACI’s own experience in investigating several low-probability events has convinced us that customers who report such problems tend to be too easily dismissed, rather than receiving the respectful assumption that they are honest and observant and reporting the problems carefully; i.e. the sudden acceleration stories related by some Toyota owners were not consistent with the floor mat hypothesis. Finally, it didn’t help Toyota’s credibility when Toyota employees were caught congratulating themselves on how they had slowed and limited the accident investigation.

Despite the above reservations, the official report by the NHTSA was that the root cause was the floor mat. Well, after several years it turns out that a detailed analysis of the electronics, as brought out during a recent trial, has confirmed that it was not just the floor mat. Key trial results are detailed in “Toyota Case: Vehicle Testing Confirms Fatal Flaws,” by Junko Yoshida in the 31 October 2013 EETimes. Here’s an excerpted summary of the problems identified:

•  Software bugs that specifically can cause memory corruption

•  Unmaintainable code complexity in Toyota’s software

•  A multifunction kitchen-sink Task X designed to execute everything from throttle control to cruise control and many of the fail-safes

•  That all Task X functions, including fail-safes, are designed to run on the main CPU in the Camry’s electronic control module

•  That the brake override that is supposed to save the day when there is an unintended acceleration is also in Task X

•  The use of an operating system in which there is no protection against hardware or software faults

•  A number of other problems

The deficiencies in the throttle design are shocking, because good rules exist for the design of safety-critical electronics (e.g., Chapter 4, “Safety Analyses,” in The Design Analysis Handbook).

The Toyota case makes one wonder how many other possibly-catastrophic flaws are lurking within the cars we drive, or in other electronics-guided machinery, due to poorly-designed safety-related systems.

Prior Toyota Unintended Acceleration Posts:

10 Nov 2009
Toyota Unintended Acceleration Causing Deaths And Injuries

20 Jan 2010
Toyota Sudden Acceleration Update: It’s Not Just Floor Mats

3 Feb 2010
Stop Driving Recalled Toyotas

5 Feb 2010
Toyota’s “Drive By Wire” Throttle System Suspected As Crash Cause

21 Feb 2010
Toyota Joins The Gallery Of Shame

9 Mar 2010
Customers Claim “Fixed” Toyotas Are Still Accelerating

9 Feb 2011
Toyota Unintended Acceleration: “No Electronics-Based Cause”: Not True and Misleading

20 Mar 2012
Toyota Sudden Acceleration: An Example Of How Not To Do A Failure Analysis

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Toyota Sudden Acceleration: An Example Of How Not To Do A Failure Analysis

P.S. IF YOU’RE DRIVING A TOYOTA, TURN OFF THE CRUISE CONTROL
(see “Toyota Sudden Acceleration Document Withheld From Feds: CNN” by Sharon Silke Carty in the 03/02/12 Huffington Post)

At a crime scene, everyone knows: don’t move the body! Investigators of electronics failures should follow the same rule.

Valuable evidence may be contained in interconnected subassemblies that are initially assumed to be “innocent.” Disconnecting cables, unplugging circuits cards, and other disturbances can cause irretrievable loss of data.

Example: After its investigation of Toyota “sudden acceleration” incidents, the National Highway Traffic Safety Administration (as well as Toyota) claimed that the electronics were not at fault. Yet the NHTSA based its conclusions, at least in part, on a postmortem that was performed on a dismantled vehicle, thereby disturbing the accelerator system’s linkages with the cruise control system.

(For an earlier comment on this issue from our Engineering Thinking blog, please see “Toyota Unintended Acceleration: ‘No Electronics-Based Cause’: Not True & Misleading“)