The potential for electronic defects in Toyota vehicles to cause sudden acceleration came under intensifying scrutiny Tuesday as both federal safety regulators and congressional leaders said they had begun new probes of the issue.
Toyota has blamed more than 2,000 reported cases of sudden acceleration in its vehicles over the last decade on floor mats and sticky gas pedals, triggering massive recalls worldwide. The automaker has insisted that it knows of no electronic defect that could cause drivers to lose control of its vehicles.
But federal safety regulators disclosed Tuesday that they had begun a "fresh review" of the electronic throttle system in Toyota and Lexus vehicles, which connect a driver's foot to the engine through sensors, computers and wires, rather than a mechanical link. Regulators are also considering civil fines against the automaker for its handling of the recall, an official said.
The action comes after a growing number of independent experts have voiced doubt about Toyota's explanation, saying it cannot account for all the reports of sudden acceleration and that part of the blame may rest with the electronic throttle system. The Times reported last fall that complaints of sudden acceleration in Toyota vehicles skyrocketed with the introduction of electronic throttles.
Although Toyota has denied that electronics are to blame, those statements came under sharp attack Tuesday by Rep. Henry A. Waxman (D-Beverly Hills) and Rep. Bart Stupak (D-Mich.), whose staffs are investigating the company.
In a letter to Toyota, they accused the automaker of telling the public one story about its engine electronics and a different one to committee investigators in recent meetings.
The letter alleges that while Toyota was assuring the public the problem involved only floor mats and sticking pedals, its executives were acknowledging to his committee's investigators that they couldn't be sure about the causes and that reports of vehicles accelerating under wide-open throttles could not be explained by sticky pedals.
Toyota representatives acknowledged to the committee that a sticky pedal might remain in a slightly depressed position, the letter said, but "they said that this would not lead to full-throttle acceleration." The letter also quotes Toyota representatives as acknowledging that it is "very, very hard to identify" the causes of sudden acceleration.
In a media blitz this week aimed at reassuring the public, Toyota executives have insisted that electronic problems are not behind the reports of sudden acceleration.
Waxman and Stupak said they wanted to see the company's documents "that substantiate this claim."
The letter also raises questions about when Toyota knew that it had a defect in its accelerator pedals. Although it has publicly said that it became aware of the problems in late October, it told the committee staff that it first learned of the issue in April or May.
Waxman is chairman of the House Energy and Commerce Committee, which plans to hold a hearing on Toyota's action Feb. 25.
Toyota spokesman Brian Lyons said the company would "continue to cooperate" with federal regulators. He did not comment on the congressional investigation.
The National Highway Traffic Safety Administration, meanwhile, said in a statement that it would meet for the first time with outside safety experts, as well as manufacturers and suppliers, to review the potential that electronic defects are part of the problem. The statement cautioned that the agency was conducting a "background examination" of the issue and that it did not have any reason to believe that Toyota vehicles have an electronic defect.
The agency acknowledged that it has done "very limited testing" of possible electronic defects, but left open the possibility that it might engage in "thorough research testing of a range of vehicles under circumstances that introduce [electronic interference] to see whether the electronic systems in those vehicles can be affected . . . in any way that causes safety problems."
The statement signals a major shift in NHTSA's position since last fall, when it told The Times that it had extensively investigated the potential for hidden electronic defects and had not found any evidence of one.
NHTSA was without an appointed chief for most of last year. David Strickland, a former congressional staffer with extensive experience in auto safety regulation, took command of the agency in late December.
The new scrutiny on electronics issues represents a key development in auto safety, comparable to the explosive investigation conducted in Ford Explorer rollovers caused by defective Firestone tires a decade ago, said Clarence Ditlow, executive director of the Center for Auto Safety.
"Toyota's unintended acceleration is going to be a watershed," Ditlow said. "It is a problem so big that NHTSA can no longer sweep it under the carpet, and they are finally going to have to look at it."
Ditlow said that NTHSA has acknowledged, in response to a recent request under the Freedom of Information Act, that it could not find any records that explain or document how it has investigated potential electronic defects in Toyota vehicles.
On Tuesday, Ditlow sent a stinging letter to Strickland asserting that the agency lacked a basis for any kind of engineering assessment of the problem.
"NHTSA can't say what it did, how it did it or what the results were," Ditlow said in the letter, a copy of which was obtained by The Times. "All across America, if not the world, Toyota owners are asking if they will be the next victim of unintended acceleration. . . ."
Separately, NHTSA issued a wide-ranging demand for information to CTS, the Indiana supplier that makes gas pedals that Toyota has said can stick. The agency is investigating whether CTS pedals sold to other carmakers may have the same problem, indicating the need for more recalls.
In an e-mail sent Monday, NHTSA asked for CTS' customer lists, testing data and information on design changes.