Runaway Toyota Prius: Feds say they can't explain
Federal government officials said they can't explain why a Toyota Prius suddenly accelerated last week.
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According to the memo, a Toyota official who was at the two-day inspection last week in suburban San Diego explained that an electric motor would "completely seize" if a system to shut off the gas when the brake is pressed fails, and there was no evidence to support that happened.Skip to next paragraph
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"In this case, knowing that we are able to push the car around the shop, it does not appear to be feasibly possible, both electronically and mechanically that his gas pedal was stuck to the floor and he was slamming on the brake at the same time," according to the memo.
Toyota has recalled millions of cars because of floor mats that can snag gas pedals or accelerators that can sometimes stick. Sikes' car was covered by the floor mat recall but not the one for sticky accelerators.
He later told reporters that he tried to pull on the gas pedal during his harrowing ride, but it didn't "move at all."
The Prius is powered by two electric motor-generators and a small gasoline engine, all connected by transmission gears. A computer, which Toyota calls the "hybrid control computer" determines what combination of motors is needed and which would be most efficient.
Craig Hoff, a professor of mechanical engineering at Kettering University in Flint, Mich., said that for the Prius to accelerate out of control, at least two systems would have to fail simultaneously. They are the sensor signal that tracks the brake and gas pedal positions when the driver presses on them and the hybrid control computers.
"The chance of them both going wrong, plus the fact that the signal is bad, it just seems very, very, very remote," Hoff said. "Could it happen? Statistically, yes. But it just doesn't seem very likely."
Several events usually combine to cause problems with cars, and it's difficult to reproduce them, Hoff said.
"It's going to make it really hard to find, because you've got to line up the multiple effects," he said.
The congressional memo said both the front and rear brakes were worn and damaged by heat, consistent with Sikes saying that he stood on the brake pedal with both feet and was unable to stop the car. But if the fail-safe system worked properly, the brakes wouldn't have been damaged because power would have been cut to the wheels.
Gomez said the best evidence that his client was frantically slamming the brakes is that a California Highway Patrol officer who was giving Sikes instructions over a loudspeaker smelled burning brakes and saw the lights on.