The fact that no trouble codes have been associated with unintended acceleration has been a sticking point in Toyota's investigation of the problem.
The press conference included five different presenters, all of whom criticized Gilbert's experiment as "unrealistic." Over and over they said the professor had "rewired the circuit" to do what he wanted it to do, which was to produce full-throttle acceleration.
In the words of Exponent principal Shukri Souri, "This was a careful and deliberate manipulation of the electrical circuit to achieve the desired result."
The most important point: Exponent showed that the same result could be made on many other vehicles without a code.
Demonstrating the connector that houses the wires where Gilbert produced two short circuits, they showed how it was unlikely such a scenario could occur in the real world. The connector contains six wires in a single row. To create the fault Gilbert demonstrated would require shorting the first wire to the fourth wire with a specific resistance, then shorting the third wire to the fourth wire, leaving the second wire and its insulation intact. It would be very difficult in the real world to duplicate the exact narrow range of resistance needed to avoid setting a code.
However, once the wires exit the connector, they are bundled together in a round wiring harness and virtually all touch each other. Exponent engineers explained that a short in either the connector or the wiring harness, would leave physical evidence, such as corrosion or damaged wire insulation. They implied that Toyota has not seen evidence of this in the cars it has examined.
The Webcast seemed carefully orchestrated to discredit Gilbert's report. At least two of the presenters noted that a specific resistance was needed to duplicate his results, not mentioning the range his report cites.
Another presenter, however, noted the communications problems between Exponent's electrical engineers and the public. That was Dr. Chris Gerdes, a professor of automotive technology at Stanford University, which Toyota hired to provide independent support for Exponent's analysis. Dr. Gerdes said he thinks Congress, regulators, and the press are misinterpreting Gilbert's report. ABC News, for instance, used Gilbert and his methodology to recreate a frightening sudden-acceleration event. (See the ABC News video.) However, Gerdes noted that the Gilbert report does not claim to show unintended acceleration, only that the throttle control circuit can be manipulated without triggering a fault.
In his Congressional testimony, Gilbert says this shows Toyota's system is not infallible. His primary conclusion is that his test should have triggered an error code. In his report, he does not claim his procedure explains how unintended acceleration occurs in the real world.
Asked by a CBS reporter whether Exponent was claiming their analysis showed electronic throttles could not produce unintended acceleration, Gerdes noted another miscommunication: between engineers and journalists. Engineers, he said, are following professional ethical guidelines when they refuse to say categorically that they have ruled out a problem. They can't make conclusions that go beyond what their actual data shows. To journalists and the public, he says, this sounds like obfuscation.
Indeed, questions about the causes of unintended acceleration can hinge on the definition of the term, as well as the data used in answering. In our studies, we have screened out complaints that clearly didn't involve unintended acceleration or clearly looked like driver error, such as misuse or accidental activation of the cruise control. The government, in its investigations, ruled out any event which lasted longer than three seconds or in which the driver reported stepping on the brakes. These different assumptions can make a huge difference both in the number of events considered and in the universe of potential causes being examined.
Consumer Reports has recommended making entries in the National Highway Traffic Safety Administration's complaints database more uniform and easily understood. (Read: "Consumers Union calls for changes to strengthen U.S. car-safety net.")
We're not in a position to say whether Dr. Gilbert's study is realistic or not, but it's clear that better communication, and agreement on just what constitutes unintended acceleration, would go a long way toward identifying possible causes.
Exponent will continue to work with Toyota on investigating potential causes for unintended acceleration, and there is no deadline set for the completion of this work.
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