A federal investigation into reports of unintended acceleration in Toyota vehicles "may have been too narrow," an influential U.S. Senator is suggesting.
Sen. Charles Grassley (R-Iowa) says that information his office has received from whistle-blowers indicates that a probe by NASA and federal highway safety officials may not have uncovered the real culprit in the incidents, which led to a massive recall of Toyota and Lexus vehicles.
The joint probe by NASA and the National Highway Traffic Safety Administration (NHTSA) concluded that Toyota's electronic throttle control system was not to blame for the incidents, which included numerous accidents, some of them fatal.
In August 2009, a California highway patrolman and his family were killed in their runaway Lexus ES 350 on a San Diego freeway. Someone calling from the car before it crashed at over 100 miles per hour said they couldn't stop it. Seconds later, it struck an SUV. Â
The Los Angeles Times reports that Grassley has written toÂ NHTSA Administrator David Strickland, asking for detailed information about the investigation -- specifically whether vehicles were tested for the presence of an electronic phenomenon known as "tin whiskers" that could have been the cause of unintended acceleration.
In February 2011, Transportation Secretary Ray LaHood announced with great fanfare that the joint investigation by NHTSA and NASA engineers hadÂ found no evidence the automaker's electronic throttle system played a part in incidents of unintended acceleration.
"There is no electronic-based cause for unintended high-speed acceleration in Toyotas," LaHood said.
Instead, the agencies said the acceleration problems were most likely mechanical in nature. They blamed floor mats that could jam the gas pedal and sticky accelerator pedals.
The NASA engineers did consider the tin whiskers phenomenon but concluded it did not play a role in the incidents.
The term is used to describe small crystalline "whiskers" that sometimes grow from electroplated tin. Under certain conditions, the whiskers could conceivably create a short circuit that "could theortetically lead" to unintended acceleration, Grassley said in his letter to LaHood.
The Times, however,Â Â quoted a Toyota spokesman as saying, "No one has ever found a single real-world example of tin whiskers causing an unintended acceleration event."
NHTSA said the agency is reviewing Grassley's letter.
Toyota has recalled more than 18 million vehicles since 2009. Five million of those recalls were to fix floor mat problems and four million were to fix gas pedals that were prone to stick.
Toyota faces hundreds of lawsuits filed on behalf of victims of accidents blamed on unintended acceleration. It has already paid $48 million in fines in three separate cases and faces potential liabilities of $10 billion or more in the cases that are still pending.
While the 2011 report exonerated Toyota's electronic throttle system, it did not directly examine the prevalence of pedals that became trapped in place by floor mats or pedals that stuck in the open position.
However, the report said that most of the incidents NASA and DOT engineers examined occurred at low speed and appeared to be caused by driver error, with the driver inadvertently stepping on the gas rather than the brake, or in some bases depressing both pedals at once.
The few high-speed incidents that have been documented were likely caused by the floor mat jamming the accelerator pedal into the wide-open position, the investigators said, basically blaming driver error for the problem.