LOS ANGELES - Crisis-hit Toyota hit back once again Monday at allegations that the electronics in its vehicles caused the problems with sudden acceleration which led to the recall of millions of vehicles.
The Japanese automaker staged a technical demonstration in which it tore apart as "unrealistic" and "contrived" a study by a vocal critic showing that crossed wires could send a false signal that would cause Toyota cars to speed out of control.
David Gilbert, a professor of automotive technology at Southern Illinois University told a US congressional investigation last month that affected Toyota and Lexus vehicles may have an electronics design flaw.
The carmaker dismissed his findings, saying he had re-engineered and rewired the signals from the accelerator pedal in order to create the flaw rather than analyzing "real world" evidence.
"If an electrical system is re-engineered and rewired it's not surprising that subsequent testing of the system may cause unrealistic results," Toyota spokesman Mike Michaels told reporters.
"Speculation is easy. Science takes a lot more effort."
Engineers from the consulting firm Exponent -- which Toyota has hired to analyze its systems for potential faults -- demonstrated how the process would create a similar result in vehicles made by General Motors, Honda, Ford, Chrysler and BMW.
"This in no way indicates a defect with this vehicle," Matthew Schwall, a managing engineer with Exponent, said as he showed how the altered circuits could send false signals.
"The only reason the engine accelerated is because we followed Mr. Gilbert's method and rewired it to do that."
The only way the fault could be created, they explained, was if the protective coverings on the wires were eroded and a specific electrical charge was created as two non-adjacent wires connected.
Not only is it highly unlikely in the real world, but it would also leave behind obvious physical evidence which has not been detected in any of the problem vehicles, the engineers said.
"You cannot rewire a circuit and expect it to behave as it was originally designed," said Chris Gerdes a mechanical engineering professor who is the head of Stanford University's Center for Automotive Research and attended the briefing at the automaker's US headquarters near Los Angeles.
Gilbert's report to congress "draws conclusions about the Toyota circuit based on tests on a different circuit" and contains "no evidence of any real world circuit malfunction," he said.
Two US lawmakers on a committee looking into the Japanese auto giant's woes asked the company Friday for documents backing up its position that electronic defects were not to blame for acceleration problems.
Toyota's demonstration was a "convincing rebuttal" which effectively proved that an electronic hardware problem is not likely at the root of the problem, said Bill Visnic, a senior editor at the automotive website Edmunds.com.
US regulators said last week that they had received more than 60 complaints from Toyota owners reporting sudden unintended acceleration despite having their recalled vehicle repaired by a Toyota dealer.
Toyota is in the process of investigating those complaints and has found that some of the incidents were a result of incomplete repairs, Michaels told reporters.
"We remain confident that if the modifications to the vehicle are deployed and done properly that they are effective," he said.
Toyota, which overtook General Motors in 2008 to become world number one automaker, has seen its reputation tarnished by a litany of complaints ranging from unintended acceleration to brake failure and steering problems.
The Japanese auto giant's president, Akio Toyoda, met Monday with Prime Minister Yukio Hatoyama, who urged the founding company scion to strive to restore confidence in its brand.
