A flaw in the design of Toyota's electronic acceleration system prevents the car's onboard computer from detecting and stopping certain short circuits that can trigger sudden speed surges, according to a professor of automotive technology, Dave Gilbert of Southern Illinois University's auto technology department.
As a result, Gilbert told ABC News, the Toyota computers will not record an error code, nor will they activate the "fail safe" system designed to shut down the power and put the car in the "limp home" mode.
"This is a dangerous condition, it is not fail safe," said Gilbert in an interview to be broadcast Monday on ABC World News with Diane Sawyer.
Editor's note: We have changed a two second insert shot in the video to the left, showing the tachometer during Professor Gilbert's demonstration.
The original insert shot was taped when Professor Gilbert demonstrated how an induced short circuit could cause the acceleration as the car was in park.
As you will see, the insert shot of the tachometer taped as the car is rolling is extremely shaky, which is why it was not originally used. The readings of the induced surge are comparable.
A question about the original shot (which clearly shows it was taped while the car was parked with the doors open) was brought to our attention by a writer at the Gawker.com website, John Cook.
"If there was this kind of fault, it will never set an error code," said Gilbert. As a result, he said, there will be "no fingerprints, no trail" when Toyota engineers inspect a car after an accident or incident of sudden acceleration.
In a statement posted on its website Monday night, Toyota said confirmed it was aware of Professor Gilbert's concerns and was prepared to evaluate his car and his methods, inviting ABC News to be present.
Toyota said what Dr. Gilbert demonstrated on ABC World News with Diane Sawyer appeared to be different than what he had originally described to Toyota's engineers.
In its statement, Toyota said based on what it understood Professor Gilbert to have described, "unintended acceleration would not occur."
Safety advocate Sean Kane, of Safety Research & Strategies, who first spotted the trend of owner complaints about "runaway Toyotas," says Gilbert's tests undercut Toyota's claims that its electronic system is not to blame for the sudden acceleration surges.
"This is clearly an electronic problem," said Kane, who is scheduled to testify Tuesday before the House Commerce Committee on the Toyota issue.
"The system is fallible, in fact, it's got some really troubling design strategies that are employed by Toyota that appear to be outside the norm. And their system clearly has a design strategy that has a very slim margin of safety."
Kane said the short circuits introduced by Gilbert in his tests and demonstrations reflect what can happen in the real world because of corrosion, moisture, and manufacturing imperfections. "Electronics don't always function the way they're supposed to," he said.
Professor Gilbert said he notified senior Toyota engineers in California of his findings last week.
"They were surprised," he said.
Toyota has consistently maintained there are "no electronic problems" connected to sudden acceleration.
Dr. Gilbert says he found the problem in four separate Toyota models -- the Lexus, Tundra, Avalon and Matrix.
"Other vehicle manufacturers have gone to great extremes," he said, to prevent the problem he claims to have found in the Toyotas. His tests on GM cars did not find a similar flaw, he said, "not even close."
Kane said the fact that the cars' onboard computers fail to detect the error could help to explain why Toyota has dismissed complaints from car owners about acceleration surges.
"We're hearing from consumers that Toyota tells them it can't possibly happen and if it did, it would set an error code. Well, in fact it doesn't," said Kane.
The company has maintained driver error, sticky gas pedals or pedals trapped by floor mats explain all of the thousands of reported incidents involving "runaway Toyotas."
In an interview with ABC News last month, the president of Toyota USA, Jim Lentz, said he was "confident" there was no electronic problem. Toyota has placed full-page advertisements in newspapers across the country making the same claim.