NEW YORK (CNNMoney.com) -- Witnesses at the first of three Congressional hearings on Toyota's recall problems testified that they believe they have found a possible additional cause of unintended acceleration in Toyotas, one that has to do with the vehicles' electronic throttle control systems.
David Gilbert, a professor of automotive technology at Southern Illinois University, said he had uncovered a potential for a short circuit that could undermine the car's built in safety checks.
"What this does is this opens the opportunity to have other problems occur without detection," he said.
Toyota Motor U.S. sales chief Jim Lentz said that an engineering consulting firm hired by Toyota, Exponent, Inc., was able to replicate the situation created by Gilbert both in a Toyota vehicle and in a competing vehicle.
Gilbert spoke shortly after Rhonda Smith, a Lexus owner who experienced an episode of high-speed unintended acceleration in her ES350. The car revved out of control shortly after she entered the highway, she said, and neither the brakes nor shifting the car into neutral or reverse brought it to a stop.
"After six miles, God intervened," she said, and she was able to bring the car to a stop.
Representatives of both Toyota and National Highway Traffic Safety Administration told her that what she had experienced could not have happened, she said.
"I was labeled a destructive lying idiot," she said.
The system used on Toyota relies on two separate sensors connected to the gas pedal and another pair connected to the throttle valve itself.
In order for the system to work each sensor in a pair has to match. If they don't match in the proper way, an on-board computer immediately senses that as a problem and the engine power is immediately reduced to idle or, in some situations, it's shut off altogether.
Gilbert said that he overrode that safety feature, which would have allowed faulty pedal signals to be sent to the engine with no problem being detected by the car's on-board computer.
Toyota has raised questions about Gilbert's tests and its application to real-world circumstances. The carmaker has invited Gilbert to demonstrate the problem for them after Toyota's own engineers were unable to replicate the situation in an earlier test.
The problem could, theoretically, be caused by a manufacturing defect in the sensors, Gilbert said.
Gilbert said he was unable to create a similar problem in cars by other manufacturers, including General Motors and Honda. Those cars use more stringent error-checking systems in their cars, Gilbert said.
"We are confident that no problems exist with the electronic throttle control system in our vehicles," Toyota Motor U.S. sales chief testified. "We have designed our electronic throttle control system with multiple failsafe mechanisms to shut off or reduce engine power in the event of a system failure."
After revealing that Toyota's consultants had been able, late Monday night, to replicate Gilbert's results, Lentz expressed skepticism that "crossing wires" reflected a real-world issue.
"Of these five attorneys who have sponsored your research how many of these law firms, right now, are suing Toyota?" Buyer asked Sean Kane, president of Safety Research & Strategies.
"I believe every one of them represents the voice of a victim of the problem we are dealing with today," Kane replied.
Ray LaHood, secretary of the U.S. Transportation Department, told the subcommittee that the National Highway Traffic Safety Administration is going to investigate the possibility that electronic defects are to blame for some of Toyota's acceleration problems.
"Under our watch we are going get into the weeds and have a complete review on the electronics," he said.
LaHood, who was named Transportation Secretary in January, defended his agency's handing of Toyota's safety problems and said the government will work to ensure the safety of American drivers.
A NHTSA administrator went to Toyota headquarters in Japan earlier this year to press the automaker's management to instigate the recalls, LaHood said. "I think they were a little safety def and we wanted to create some listening devices for them."
In a letter addressed to Lentz Monday, Oversight and Investigations subcommittee chairman Rep. Bart Stupak (D-Mich.) wrote that his committee's preliminary review of 75,000 pages of Toyota's internal company documents raises significant concerns. In particular, Toyota boasted of saving $100 million by dodging a more extensive recall of the Toyota Camry and Lexus.
In response, Lentz said in prepared testimony that, "Put simply, it has taken us too long to come to grips with a rare but serious set of safety issues, despite all of our good faith and efforts. The problem has been compounded by poor communication both within our company and with regulators and consumers."
He goes on to say that Toyota's investigation of customer complaints focused on technical issues, failing to efficiently analyze and respond to information about sticking accelerator pedals.
"We acknowledge these mistakes, we apologize for them and we have learned from them," Lentz says in the remarks. "We now understand that we must think differently when investigating complaints and communicate faster, better and more effectively with our customer and our regulators."
He adds that Toyota's recent recalls of certain 2010 Prius and Lexus hybrids and 2010 Tacoma trucks exemplifies the automaker's revised approach. Plus, he explains that some of Toyota's 1,500 dealers are staying open 24 hours and have already repaired close to 1 million recalled vehicles.
Rep. Phil Gingrey (R-GA) asked Lentz if, in light of all the recent news about Toyota, there would be any more "bombshells" coming from the carmaker.
"God I hope that there aren't any more. There have been enough bombshells," Lentz said. "Let's get back to the good old days of 2009, and I didn't think I'd ever say that."
Toyota president Akio Toyoda, who is scheduled to testify before the House Committee on Oversight and Government Reform on Wednesday, will lead a "top-to-bottom review" of Toyota's operations, Lentz added.
Several witnesses at Tuesday morning's hearing are expected to testify about their suspicions that a software issue in the car's computerized throttle system may be to blame in some cases of unintended acceleration.
Documents reviewed by the Energy Committee call into question the thoroughness of Toyota's investigations.
During opening statements at the start of Tuesday's hearings, several Representatives also questioned NHTSA's ability to deal with possible software issues, noting that agency lacks technical expertise in computerized automotive systems.
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