Toyota Motor Corp remains confident that its electronic throttles are sound and not behind instances of unintended acceleration that led to huge recalls, federal investigations, and lawsuits, the company's U.S. sales president said on Wednesday.

In written testimony submitted to Congress before a Thursday hearing, Jim Lentz also said Toyota had serviced more than 3.5 million vehicles or roughly half the vehicles recalled between October 2009 and January 2010 for equipment and mechanical issues linked to the acceleration problems.

We are taking major steps to become a more responsive, safety focused organization, Lentz said in remarks to the House of Representatives Energy and Commerce Committee. Our entire company has mobilized to ensure that Toyota vehicles are safe and reliable for our customers.

On Tuesday, Toyota paid a $16.4 million fine to settle allegations by U.S. regulators that the company had been slow to act on one of the recalls.

Toyota shares closed up 14 cents at $75.71 on the New York Stock Exchange on Wednesday.

Some members of the Energy and Commerce Committee are not convinced that Toyota's fixes in recalled vehicles address all questions about unintended acceleration. The committee has demanded information about Toyota's electronic throttle systems and whether they could be at the root of acceleration problems that authorities have said could be linked to dozens of crash deaths since 2000.

Toyota has never discovered or been provided with any evidence that (electronic throttles) can cause unintended acceleration in a real world scenario, Lentz said in his testimony.

Toyota has hired an engineering consulting firm, Exponent Inc, to analyze its throttle systems.

The National Highway Traffic Safety Administration (NHTSA) reopened an investigation into Toyota's throttle systems and unintended acceleration after members of Congress and safety advocates questioned whether previous reviews had been thorough. NHTSA is working with experts from the U.S. space agency NASA to analyze the throttles.

The analysis will be reviewed by an independent scientific committee before the NHTSA decides how to proceed.

NHTSA administrator David Strickland told the Senate Commerce Committee at a hearing on Wednesday the analysis and review would likely take more than a year.

Safety legislation prompted by the Toyota recalls that is working its way through Congress would set minimum requirements for vehicle electronics, including throttle systems.

It would also mandate safety systems that would allow the brakes to override acceleration in all cases in which the driver seeks to stop the vehicle.

Consumers have complained over the years to regulators about Toyota vehicles that accelerated without warning and would not stop.

In a case last August that prompted sharp government scrutiny and led to an October 2009 recall, a California patrol officer and three of his family members were killed in a high-speed Lexus crash that authorities believe was caused by a loose floormat that jammed the accelerator pedal.

Lentz said in his testimony that brake override would be available across Toyota's product line by the end of this year. He said it would be standard on new models in the United States and that seven existing models would be retrofitted with it.

Toyota's recalls involved floormats and accelerator pedals that would not spring back as designed. Lentz said the company had completed 70 percent of the so-called sticky pedal modifications and 30 percent of the floormat cases.

It has also completed about 80 percent of the antilock brake software upgrades in 147,500 recalled Prius and Lexus models, Lentz said.

(Reporting by John Crawley; Editing by Gary Hill)

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