Rep. Bart Stupak, chairman of the House Energy and Commerce Committee's subcommittee on oversight, said, "We don't know whether electronics plays a role in sudden unintended acceleration and Toyota doesn't either," the Detroit Free Press reported Friday.
Rep. Henry Waxman, D-Calif., said lawmakers could "find no basis" for assertions that Toyota had extensively tested its vehicles.
"Toyota's assertions may be good public relations, but they don't appear to be true," Waxman said.
Under questioning, Jim Lentz, the head of Toyota's U.S. sales, said brake override systems installed in new Toyotas were designed to shore up "customer confidence." Regarding safety, Lentz said, "I think for some people it could be safety. I can't speak for all consumers. I can't say 100 percent it's necessarily going to make the car safer."
Brake override systems are designed to cut engine power when a driver steps on the brakes so that unintended acceleration can be stopped quickly.
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