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Understanding Toyota Sudden Acceleration

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As a materials and manufacturing engineer with decades of experience with failure analysis of manufactured products, and as an owner of a Toyota vehicle, I am saddened by the lack of expertise and insight shared with Congress and the public about the sudden acceleration problem.

When products fail due to a systemic design, materials or manufacturing flaw, large and statistically significant levels of problems emerge fairly rapidly. This is definitely not the case with the Toyota problem. With many millions of Toyota models on which even more millions of miles have been driven, if there had been an inherent materials or manufacturing design defect, then we would have seen untold thousands of cases of sudden acceleration. It literally would have been virtually a daily event happening all over the country in many Toyota models. But, in fact, little more than 1,000 Toyota and Lexus owners have reported since 2001 that their vehicles suddenly accelerated on their own. This is a tiny, minuscule percentage of Toyotas.

This infrequent runaway car problem is not analogous to a serious case of bacterial contamination of a major food product causing many thousands of cases of food poisoning in a relatively short period. It is even more difficult to find the cause of.

Understanding this nature of defects also means that the so-called solutions of replacing floor mats and gas pedals are sheer nonsense. Indeed, it did not surprise me to read today that there have already been cases of sudden acceleration in cars that had received fixes by Toyota. More than 60 Toyota owners have complained to the National Highway Traffic Safety Administration about cars already repaired under the two major Toyota recalls, saying they aren’t fixed and their throttles can still race out of control.

While recognizing the agony and suffering of sudden acceleration accidents and deaths it is also necessary to appreciate the statistically rare occurrences of this problem. Only by doing so is it possible to understand that the ultimate explanation – and solution – to the sudden acceleration problem will be a non-systemic flaw or defect in a critical component. In other words, either a random defect in a material or some unusual and infrequent deviation in a manufacturing process of some critical component. Only such a situation can logically explain so few sudden acceleration problems in so many millions of cars being operated for many more millions of hours and miles.

In my professional opinion, the likely scenario is a defect in a semiconductor chip used in the electronic control system. A defect that was caused by some infrequent flaw in a raw material or manufacturing process that would not show up in routine quality control testing of raw materials or components. That so many different Toyota models over many years have been found defective signifies the likelihood of a particular problem component made in a specific factory that has been used for quite a while. Moreover, the defect obviously does not ordinarily impair vehicle performance but only manifests itself under some infrequent conditions, as yet undetermined.

Rita Taylor of Fort Worth, Texas experienced runaway acceleration, took her car to a Toyota dealer, and had the floor mats removed. A few months later she had another frightening runaway episode. Ditto for Eric Weiss in California, who also had a second episode months after the first one and after removing the mats. Others who have not died and kept using their Toyotas have also had repeat events. Thus, perfectly normal vehicle performance is possible between runaway events. Others who have not died and kept using their Toyotas have also had repeat events.

Make no mistake, the precise cause of such a sporadic event is incredibly difficult to pin down and even more difficult to remedy. An extremely intense and costly investigation is necessary. It is the classic needle-in-the-haystack problem.

If my thinking is correct, then it is sheer folly to believe that replacing floor mats or gas pedals can solve the sudden acceleration problem. However, there is one aspect to the sudden acceleration problem that also is crystal clear and, in some ways, even more aggravating than the acceleration problem. This is the absence of an override system that absolutely prevents fuel being fed to the engine when brakes are employed while a car is accelerating. It is gratifying that the federal government is seriously considering requiring such an override system in all vehicles. An effective override system might, in the long run, be a faster and more cost-effective solution than chasing-the-defect strategy, especially for retrofitting many millions of vehicles.

Alternatively, finding the cause of the sudden acceleration problem requires a standard failure analysis methodology, namely to obtain absolutely every Toyota vehicle that has experienced sudden acceleration. Then meticulously examine through microscopic and other types of analysis and testing all critical components of the electronic system (called by Toyota the Electronic Throttle Control System with intelligence). Think of it like an autopsy.

This does not appear to have been done. To the contrary, the firm hired by Toyota tested several ordinary vehicles and components. One of the primary authors of the Exponent report said they did not examine any vehicles or components that had the unintended accelerations. This makes no sense whatsoever if the defect is rare and, therefore, its finding that there was nothing wrong was meaningless. Worse, it was a deception and distraction.

[The author has a Ph.D. in Materials Engineering and was formerly a full professor of metallurgical engineering at the University of Wisconsin, Madison and a consultant for many corporations, such as IBM, Texas Instruments, Polaroid, and RayOVac, and has served as an expert witness in many legal proceedings.]
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About Joel S. Hirschhorn

Formerly full professor Univ. of Wisconsin, Madison, and senior official Congressional Office of Technology Assessment and National Governors Association. Author of four nonfiction books and hundreds of articles.
  • zilla

    Hi Joel, thank you for a more balanced take on the acceleration problem than what can be usually had online. I would have to draw everybody’s attention to the fact that there are OTHER manufacturer’s sudden acceleration cases and it would keep the discussion even more balanced and productive if it is acknowledged that there are also Volvo sudden acceleration problems, GM sudden acceleration problems as well as Ford sudden acceleration problem. And that’s only what I have been able to come across online in recent months. I am 100% sure you can come up with a wildcard like “X sudden acceleration problem” and then substitute X with any manufacturer’s name out there and you will find references to existing cases.
    Going after Toyota – the most successful automobile manufacturer in the world – looked like a higher return game for everyone involved and so the discussion has been skewed from trying to find how to deal with computer bugs that can directly kill humans (here I completely and wholeheartedly agree with you) to how to punish Toyota for leaving GM and Ford in the dust.
    What we see now is just a beginning of a whole new era in computer de-bugging. Up to now it was impossible to imagine a situation where a computer programmer can be sued for not cleaning all the bugs from the finished product. Blue Screen of Death, anyone? I am sure there have already been cases, in the military and dangerous industries at least, where a computer bug did kill people but they have never been publicized to the degree that Toyota’s sudden acceleration has. I think we can turn this issue into a very productive nation-wide discussion on the effect that computers, and by extension, computer bugs, can have on human lives.
    We just have to make Toyota (and have other manufacturers follow) acknowledge that the issue is not a wrong size piece of rubber but a more complex computer-related problem.

    Peace everyone and stay safe out there!

  • Joel S. Hirschhorn

    zilla: true enough, there have always been reports of sudden acceleration for virtually all makes of cars. But the number of Toyota cases in recent years is totally beyond anything reported for other makes – orders of magnitude greater. Even Toyota never attempted to argue that what was being reported for its brand was just like everyone else’s numbers. Another point: over many years sudden acceleration has very frequently been caused by drivers hitting their gas pedal rather than their break pedal. I think Toyota owners, like me, have every right to feel betrayed because what Toyota is now saying makes no sense. Finding an electronics defect seems like something they just do NOT want to confront.

  • STM

    Sudden acceleration ….

    I’ll give you sudden acceleration. And it won’t be a problem, either.

    We have an answer to this in Australia, especially to the issues now confronting the Prius: don’t buy one.

    Buy a dirty big, stonking Ford or Holden rear-wheel drive V8 (turbocharged if possible) and go easy on the accelerator pedal until you’re out of town on the open road and you can get some real growl happening.

    Alternatively, do what the Europeans do: buy a hotted up diesel. Geez, there’s some mid-range torque happening in those.

    The sooner this planet’s petrol supplies are all used up, the sooner we’ll a) have all the car manufacturers getting serious about prodviding decent electric cars, and b) end the situation that now sees us all being held hostage to the major oil-producing nations.

    Do your bit!

    I also heard on radio here in Oz this morning that Toyota was still blaming sticky floor mats for some of the accelerator problems.

    On a serious note, Toyota really needs to address in a hurry whatever it is that’s really going on, or my scenario will become reality. Partly, that’s already a risk of happening here.

    In this country, Ford and Holden (GMH)will doubtless be laughing all the way to the bank right now, especially as would-be buyers of big 6-cylinder or V8 Toyota and Lexus models go shopping for cars with the other two big manufacturers instead.

  • Mike

    If there was a non-systemic flaw in the electronics system wouldn’t sudden acceleration also be seen in toyotas with denso pedals? As far as I know, only the CTS pedals are susceptible to the problem. This implicates the CTS manufacturing process or the Toyota specifications for the CTS pedals. And since we’re dealing with a non-systemic issue obviously we are dealing with CTS manufacturing correct?

  • Brian aka Guppusmaximus

    Hmmm… I guess Ford lucked out because when they had their recalls on everything (which seemed like every other month)from the tires (disintegration), fuel tank explosions, massive roll-overs and all the way to the seat belts the internet wasn’t around to give their issues the free spotlight.

  • the most complex part in these cars is very likely the control system, the software that is basically running the vehicle.

    i’ve written software for control systems, from semiconductor manufacuring to entertainment to embedded medical devices. the truth is that even the most rigid and seemingly complete testing methodologies can allow bugs to lurk. i’m betting that’s where the problem is.

  • Dale

    Toyota began using “drive-by-wire” technology in their 2002 vehicles and knew as early as 2004 that customers were being killed in sudden acceleration crashes. I put my money on something in the electronic throttle failing under certain circumstances, or even at random. Toyota blaming the floor mats is just a lame excuse they used to inexpensively reassure their customers that everything was OK.

    The independent firm Toyota hired to investigate the electronic throttles allegedly only tested cars that had NOT experienced the sudden acceleration syndrome. Duhhhhh!

    The real truth came out a few days ago when a Toyota exec admitted it was a CULTURAL problem. He stated the Japanese top brass at Toyota would not admit failure, and tried to divert attention elsewhere.

    As in any electronic component, faulty software, a problem in the manufacturing process or raw materials that don’t meet specs can cause random problems that can only be found while the part is “broken”. Anyone who drives a car today places their life in the hands of a few onboard computers.

    Yes, other manufactures have occasional sudden acceleration problems, but nowhere near the numbers that Toyota is experiencing.

    The sad thing here is that people, loyal Toyota customers in fact, are DYING in these accidents.

    Recently a CHP Police Officer, along with his family, died in a fiery crash of his personal Toyota Prius near San Diego after dialing 911 from the vehicle and reporting that his throttle was stuck and his car was going 90 mph and nearing the end of the highway.

    Just today the driver of another Toyota Prius in San Diego called 911 to report his Prius throttle was stuck and he was going 95 mph and couldn’t stop. Luckily a CHP officer was able to position his cruiser in front of the Prius and brake it to a stop after the driver burned up his brakes and emergency brake in slowing the car to 55 mph. The driver said he took his car to the Toyota dealer two weeks ago and they told him it had not been recalled. See it here.

    The second url is the 911 call from the driver of a Lexus that the throttle was stuck at 90mph. Less than 60 seconds later, the Lexus was involved in a fiery crash at an intersection, killing the entire family inside.

    It is time to call out Toyota and get them to expose what knowledge they do have of the cause of these failures. Get a team of engineering experts to work and find the cause and come up with a quick, but effective fix. One more life lost is too many and Toyota needs to take responsibility here!


    UPDATE: A $1,000,000 bounty has apparently been offered by automobile organization Edmunds, Inc. to find the Toyota problem and fix it.

    Claims are being made that in cost-cutting measures last year, Toyota outsourced the manufacture of its CCM (Computer Control Modules) to a new, second-source vendor and sufficient compatibility controls may not have been established.

    Word is that the two wiring harnesses do not have compatible plugs. If this is true, they may not have to look too far for the true cause of these failures. Let us pray that they find it soon….

  • Brian aka Guppusmaximus

    @ 7,

    Ugh… Could you please spare us the Michael Moore Propaganda tone in your conspiracy theory style comments. You react as if cars have never had fatal flaws and that Toyota must be behind some plot to kill off Humans. Get over yourself! Toyota has nothing to gain from killing their clientele. Imagine if this was a problem for GM… Holy Shit, we’d seriously be fucking screwed.

    Honestly, I think Mark was correct in stating it is probably a software / firmware issue considering that “Drive-by-Wire” is basically a computer of sorts and, imo,when you incorporate computers into such a simple mechanical process, it has the potential to malfunction (even though I love computer tech).

  • Joel S. Hirschhorn

    Of course it is NOT in Toyota’s interest to kill and frighten their customers. BUT, companies all too often make incredibly stupid mistakes and the way Toyota has handled this problem has been totally moronic. Not to pursue standard failure analysis methods is by itself criminally negligent at worse and totally stupid at best. I think some idiots in Toyota did some calculations and concluded that it would cost too much to find and fix the electronics problem OR that they simply did not know how to fix the problem!!!!

  • I would be interesting, Joel, to learn whether the accelerating system, or important elements thereof, has not come from one and the same supplier.

    That would explain the prevalence of the problem across a great many makes and models.

    Do you have any info on that? To the best of my knowledge, no one thus far has inquired into such a possibility.

  • I watched this unfold and still don’t get it. I’ve been driving a Prius for five years, and LOVE it. I would never give it up. I figured it wasn’t the floor mats, I have double floor mats in my car and the gas pedal functions fine.

    I did have one of those runaway Fords though. It would pop itself out of park and into reverse. Scary.

    I’m no scientist, but I hope they figure it out.

  • Mike

    No one is answering the obvious question here:

    If it’s a software/electronics issue, then why aren’t Toyotas with Denso pedals experiencing the same issue? As far as I know, only the CTS pedals are having the sudden acceleration problem…

  • max

    @ Brian aka Guppusmaximus. the problems you listed on ford were drawn out. first of all the tires, was linked to the vehicle roll overs. but ford did not manufacture the tires, they were made by firestone. once ford switched the tires, the problems disappeared, no more roll overs or tire blow outs. you might want to look at toyota ball joint failures leading roll overs. as for the fuel tanks, im sure you mean the pinto. well even today if any car is hit hard enough it will cause fuel to leak any where, and chances are the impact would kill you if your hit that hard. its not like pintos were causing accidents. the japanese are to thank for the small cars, and thats the price you pay. as for the seat belts, i think you might be talking about the one ford did because people got food jammed in the seat belts and this caused them not to work proper. but is this fords fault some people are messy pigs?

    how about toyota’s frame rust, causing them to rust right in half and lose spare tires going down the freeway.

    do me a favour and read the 70 page report titled “the toyota you dont know” you will be able to find it with a google.

  • max

    at mike. the denso pedals are experiencing just as many sudden acceleration. toyota’s luxury lexus models as well as many other toyota’s use the denso, they have been recalled to. so either their is a problem with both pedals, or more likely its in the electronics. you also might find it interesting that toyota partially owns cts and the pedal is a toyota design. toyota fans started the rumor blaming americans. you should know that toyotas are not made here, they are built in japan. they are only ASSEMBLED here. you too need to read the report i lised above, as well as everyother american destroying the north american economy. please educate your selves. dont be the typical loyal toyota consumer, dont believe everything toyota tells you, you should be asking more questions.

  • max

    before anyone says the lexus recall was for the floormat. dont bother, because the floormats is a cover up. if it was that simple the police officer who died would have figured it out. watch the phone call. he says “our accelerator is stuck”. do you people really believe if it was the floormat a man trained for high speed pursuits would have crashed? hmm. how about all the other reports of it happening in lexus models? some of them even had the floormats in the trunk as instructed by toyota…

    you be the judge.

  • Tom

    So what we can learn from this is that vehicles using manual shift gear sticks are safer and that Toyota is solely to blame?

    A lot of other big corporations, governmental organizations and even smaller businesses can learn from Toyota a thing or two about accountability. Now it is time for Toyota to brace up and take social and business responsibility a notch up higher should it wishes to stay as one of the leaders in the automotive industry and be recognized as one.

  • Barry Zern

    I had a sudden acceleration incident with my Lexus 7 years ago. From the way it happened the most likely cause was from the computer system. Toyota said the cause was floormats, which never made any sense. It never happened again and fortunately I knew to get the transmission out of Drive otherwise there would have been a serious accident. So I was “relieved” to hear years later that it wasn’t just me thinking it was in the computer system.

    Now with the current finding I am very disappointed that apparently the victims claims are not being recognized for what some of them are.