DETROIT - A U.S. Senator is questioning whether the government thoroughly investigated electronic gremlins that could have caused Toyota vehicles to accelerate unexpectedly.
In a letter sent Thursday to the National Highway Traffic Safety Administration, Republican Sen. Charles Grassley says key questions remain unanswered about what caused Toyota's unintended acceleration problems, despite investigations by NHTSA and NASA that found electronic defects weren't to blame.
Grassley questions whether a phenomenon called "tin whiskers" inside the gas pedal assembly or other electronics could be a cause, citing information sent to his office by whistleblowers. The microscopic whiskers can sprout from solder on electronic devices, changing the flow of electricity and causing glitches. Grassley asked the agency for its position on tin whiskers as a possible cause of Toyota's problems, and to give him all information it gathered about the phenomenon.
Information from the whistleblowers "raises concerns that the scope of the NHTSA and NASA investigations may have been too narrow," Grassley wrote.
Starting in 2009, Toyota was plagued by numerous complaints that its cars accelerated on their own, causing crashes, injuries and even deaths. The company eventually recalled more than 14 million vehicles worldwide to fix problems with sticky gas pedals and floor mats that could trap the gas pedals. Although NHTSA and NASA found no evidence of electronic problems in a February 2011 report, the recalls tarnished the company's reputation for reliability and cut into sales. Only recently has Toyota shown signs of recovering.
NHTSA said it will review Grassley's letter and respond to it. Agency spokeswoman Lynda Tran said in a statement that sticking accelerator pedals and gas pedals trapped by floor mats are the only known causes of Toyota's unintended acceleration. Reports on NHTSA's investigation say that "tin whiskers" are rare, and even if they cause electrical shorts, they would not affect braking or cause cars to accelerate wildly.
NHTSA only knows of four occurrences of tin whiskers in 1.7 million Toyota Camry midsize vehicles, she said. The whiskers weren't involved in any crashes, and in each case, the cars' fail-safe mechanisms worked and the owners brought them in for repairs, according to Tran.
Toyota also said that scientific evidence has confirmed that there are no problems with its electronic controls, and that there is no data to show that whiskers are more prevalent in Toyota vehicles than those of other automakers.
"No one has ever found a single real-world example of tin whiskers causing an unintended acceleration event," company spokesman Brian Lyons said in a statement.
But Grassley says in his letter that NASA found nearly 9,700 customer complaints about unintended acceleration from 2000 to 2010, and the number likely is far larger because many incidents go unreported. He also questioned why NHTSA relied on NASA engineers and asked if NHTSA lacks the expertise needed to investigate unintended acceleration.
"This is a serious issue," he wrote, asking NHTSA to respond to his questions by July 26.
Toyota's acceleration problems waned for more than a year until late last month, when NHTSA asked it to recall 154,000 Lexus RX 350 and RX 450H SUVs from the 2010 model year. The agency said floor mats could cause unintended acceleration and told owners to remove the driver's side mats until the problems are repaired.
NHTSA also said it has asked Toyota for information about the SUV problems to see if it reported the problems quickly enough. In 2010 and 2011, Toyota paid a record $48.8 million in fines to the government for failing to promptly alert regulators to safety problems.
Lyons said Toyota gave NHTSA information about the SUVs in a timely manner after investigators asked for it.