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  • Toyota Calls In the Engineers to Help Refute ABC News Report

Toyota Calls In the Engineers to Help Refute ABC News Report

Toyota's Intended Rebuttal

Kim Reynolds
Mar 9, 2010
If you've been surfing the Web today, you've probably already seen this morning's reports from the mainstream media detailing Toyota's show-and-tell rebuttal of the high-profile claims made by Dr. David Gilbert of Southern Illinois University-Carbondale. If you haven't, the bullet points are that today a panel of technology experts, including Dr. Chris Gerdes, associate professor from Stanford University's Center for Automotive Research (full disclosure -- which Toyota helps to fund) along with Matthew Schaw, Subodh Medhekar, and Shukri Souri of Exponent, an independent engineering analysis outfit hired by Toyota, and Kristen Tabar (actually of Toyota) demonstrated with Xacto knifes, resistors, and jump wires how Dr. Gilbert achieved his proposed simulation of the alleged Toyota pedal/unintended acceleration phenomenon.
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Their point was to demonstrate that the Gilbert effect doesn't just happen. It requires some extreme and deliberate fooling with the electronics, and while always being polite to their fellow engineer, they didn't hesitate to deride Gilbert for effectively reengineering the pedal and then failing to explain how this situation could ever possibly be duplicated in the real world. To my eyes, Dr. Gilbert's hypothesis looked well and truly filleted. And putting a knife through its heart, the Exponent people performed Gilbert's manipulation on the pedals of a Ford Fusion, a Subaru Outback and a BMW, right before our very eyes. And when the proper contacts were made -- guess what? -- each car's revs similarly raced out of control. There was also an analysis of footage shown during a recent ABC News segment on the Toyota brouhaha (made with the aid of the good Dr. Gilbert) that was obviously doctored for dramatic effect (it's since been re-edited on the ABC Web site). And oh, did the Toyota team happen to note that Dr. Gilbert also receives funding from trial lawyers. Um, yes they did. I didn't know Toyota also builds steam rollers.
But argument-flattening aside, I found it illuminating was to see exactly what the heck Dr. Gilbert actually did.
Basically, these pedals contain twin, independent circuits for measuring pedal angle. Each one employs three wires, each its own voltage supply, ground, and a third wire that carries a signal voltage associated with the pedal's angle. Six wires in total. The two signal voltages vary linearly with throttle angle, but are intentionally different from each other (offset) with one ranging from 0.8 volt at closed throttle to about 4 volts at open throttle, the other going from 1.8 volts to about 5 volts. Each signal is monitored such that if either stays outside a certain (tight) voltage relationship to each other the system falls into limp-mode, letting you drive out of any dangerous traffic situations and registering an error code.
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What Dr. Gilbert did was to first place a 200-ohm resistor between the two signal voltage wires (that's exactly what's needed to replicate their signal wire's engineered-in voltage difference) and then short the supplied 5 volts to the signal voltage wire that, when working normally, isn't surprised to see 5 volts at wide-open throttle. Voila - with the masking effect of the 200-ohm resistor added, the signals from both circuits appear to be requesting full power. And the engine revs like mad.
Getting this to happen requires the circuit to first acquire this 200-ohm resistance between two wires that, at least on the pedal end of things, are physically separated by two other wires and their insulation. How could this occur in the real world? Well, it doesn't look like it could. A plausible (but yet to be seen) culprit, a gradual corrosion, would be expected to develop slowly, starting off at a very high resistance before gradually lowering to the magic 200 ohms value as the corrosion increased. This would be noticed by the computer almost instantly. Likewise would be a gross short, which would offer much less than the 200-ohm number. What are the chances of an exact, 200-ohm resistance suddenly appearing out of nowhere? Good if it's created by an electrical engineer funded by trial lawyers. The subsequent short to a 5-volt power source, necessary to complete the effect, simply borders on the miraculous.
With all that said, what wasn't addressed was what might be going on elsewhere as this bundle of wires arrives at the computer module, its electronics, and software and what happens to all of it under the influence of electromagnetic radiation. Asked about this, the Exponent engineers only said that their investigation is ongoing, but nothing unusual has been spotted thus far. A Toyota representative was blunter, saying they are confident that there are indeed no ghosts in the machine. (Presently, Toyota can test EMI effects only on the component and system level in the U.S., with full-vehicle testing being done entirely in Japan -- though a full-vehicle facility is presently under construction in Ann Arbor).
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A couple other tidbits that caught my attention were Toyota's statement that, while they haven't yet had an opportunity to examine many of the cars that have allegedly gone throttle-crazy since the pedal modifications and floormat updates, what they've seen so far suggests faulty pedal modification by service technicians. Takeaway? Personally, if I had a recalled Toyota, I'd wait a bit for the technicians to get some rest before they mess with my pedals.
The other was the observation by Stanford's Dr. Gerdes regarding Toyota's eyebrow-raising statement that they can't rule out software, or some other mysterious source, as a cause of throttle misbehavior. As Gerdes noted, this is simply an artifact how engineers speak. They're mentally trained to address precisely the data they have. And no more. In other words, if they were they asked if flea-size black holes, drifting in from the Andromeda Galaxy, have an affinity for visiting Toyota engine controls, with no data to rule it out, their answer would probably be "It's possible" - and the news media would collectively gasp, of course.
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A sad consequence of all this is that, in the future, we might not get to enjoy a frank presentation such as today's, delivered by thoughtful, but sometimes misunderstood, engineers. Instead, everything we'll hear in situations like this will be crafted by polished, snaky, spin-meisters. And as a naive, suspicious, and easily frightened public, maybe that's exactly what we'll deserve.



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