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Data point to Toyota's throttles, not floor mats

Amid widening concern over acceleration events, Toyota has cited 'floor mat entrapment.' But reports point to another potential cause: the electronic throttles that have replaced mechanical systems.

November 29, 2009|By Ken Bensinger and Ralph Vartabedian

Eric Weiss was stopped at a busy Long Beach intersection last month when he said his 2008 Toyota Tacoma pickup unexpectedly started accelerating, forcing him to stand on the brakes to keep the bucking truck from plowing into oncoming cars.

Toyota Motor Corp. says the gas pedal design in Weiss' truck and more than 4 million other Toyota and Lexus vehicles makes them vulnerable to being trapped open by floor mats, and on Wednesday, it announced a costly recall to fix the problem.

But Weiss is convinced his incident wasn't caused by a floor mat. He said he removed the mats in his truck months earlier on the advice of his Toyota dealer after his truck suddenly accelerated and rear-ended a BMW.

"The brakes squealed and the engine roared," the 52-year-old cabinet maker said of the most recent episode. "I don't want to drive the truck anymore, but I don't want anyone else to, either."

Amid widening concern over unintended acceleration events, including an Aug. 28 crash near San Diego that killed a California Highway Patrol officer and his family, Toyota has repeatedly pointed to "floor mat entrapment" as the problem.

But accounts from motorists such as Weiss, interviews with auto safety experts and a Times review of thousands of federal traffic safety incident reports all point to another potential cause: the electronic throttles that have replaced mechanical systems in recent years.

The Times found that complaints of sudden acceleration in many Toyota and Lexus vehicles shot up almost immediately after the automaker adopted the so-called drive-by-wire system over the last decade. That system uses sensors, microprocessors and electric motors -- rather than a traditional link such as a steel cable -- to connect the driver's foot to the engine.

For some Toyota models, reports of unintended acceleration increased more than fivefold after drive-by-wire systems were adopted, according to the review of thousands of consumer complaints filed with the National Highway Traffic Safety Administration.

Toyota first installed electronic throttles in 2002 model year Lexus ES and Camry sedans. Total complaints of sudden acceleration for the Lexus and Camry in the 2002-04 model years averaged 132 a year. That's up from an average of 26 annually for the 1999-2001 models, the Times review found.

The average number of sudden-acceleration complaints involving the Tacoma jumped more than 20 times, on average, in the three years after Toyota's introduction of drive-by-wire in these trucks in 2005. Increases were also found on the hybrid Prius, among other models.

Toyota spokesman Brian Lyons said the automaker could not explain the trend. But Toyota has consistently held that electronic control systems, including drive-by-wire, are not to blame.

"Six times in the past six years NHTSA has undertaken an exhaustive review of allegations of unintended acceleration on Toyota and Lexus vehicles," Toyota said in a statement this month. "Six times the agency closed the investigation without finding any electronic engine control system malfunction to be the cause of unintended acceleration."

NHTSA officials have consistently said they have not found any electronic defects. "In the high-speed incidents, which are the type of crashes in which death or serious injury is most likely, the only pattern NHTSA has found to explain at least some of them are pedal entrapment by floor mats," a spokeswoman said in a written statement.

Toyota has been under a spotlight since the San Diego crash, in which the driver's desperate efforts to stop the car were recorded on a 911 emergency call made by a passenger.

After that incident, The Times reported that sudden-acceleration events involving Toyota vehicles have resulted in at least 19 deaths since the introduction of the 2002 model year. By comparison, NHTSA says all other automakers combined had 11 fatalities related to sudden acceleration in the same period.

Independent electronics and engineering experts say that the drive-by-wire systems differ from automaker to automaker and that the potential for electronic throttle control systems to malfunction may have been dismissed too quickly by both Toyota and federal safety officials.

Unlike mechanical systems, electronic throttles -- which have the look and feel of traditional gas pedals -- are vulnerable to software glitches, manufacturing defects and electronic interference that could cause sudden acceleration, they say.

Ask the computer

"With the electronic throttle, the driver is not really in control of the engine," said Antony Anderson, a Britain-based electrical engineering consultant who investigates electrical failures and has testified in sudden-acceleration lawsuits. "You are telling the computer, will you please move the throttle to a certain level, and the computer decides if it will obey you."

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