The US Department of Transportation has ruled out electronic faults as the cause of unintended acceleration in Toyota vehicles.

The announcement followed a 10-month study that enlisted NASA engineers with expertise in areas such as computer controlled electronic systems, electromagnetic interference and software integrity to conduct new research into whether electronic systems or electromagnetic interference played a role in such incidents.

“NASA engineers found no electronic flaws in Toyota vehicles capable of producing the large throttle openings required to create dangerous high-speed unintended acceleration incidents,” the DoT said in a statement.

“The two mechanical safety defects identified by NHTSA more than a year ago – ‘sticking’ accelerator pedals and a design flaw that enabled accelerator pedals to become trapped by floor mats – remain the only known causes for these kinds of unsafe unintended acceleration incidents. Toyota has recalled nearly 8m vehicles in the United States for these two defects.”

US transportation secretary Ray LaHood said, “We enlisted the best and brightest engineers to study Toyota’s electronics systems, and the verdict is in. There is no electronic-based cause for unintended high-speed acceleration in Toyotas.”

“Toyota welcomes the findings of NASA and NHTSA regarding our electronic throttle control system with intelligence (ETCS-i) and we appreciate the thoroughness of their review,” the automaker said in a statement.

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“We hope this important study will help put to rest unsupported speculation about Toyota’s ETCS-i, which is well-designed and well-tested to ensure that a real world, uncommanded acceleration of the vehicle cannot occur.”

Toyota said electronic throttle control systems have long been standard across the automobile industry, and they provide great benefits to consumers. Its own system has performed reliably in more than 40m cars and trucks sold around the world, including more than 16m in the US and the system had also made possible significant safety advances such as vehicle stability control and traction control.

The NASA engineers evaluated the electronic circuitry in Toyota vehicles and analysed more than 280,000 lines of software code for any potential flaws that could initiate an unintended acceleration incident.

Mechanical components were scrutinised and engineers bombarded vehicles with electromagnetic radiation to study whether such radiation could cause malfunctions resulting in unintended acceleration.

Toyota vehicles were also tested to determine if there were any additional mechanical causes for unintended acceleration and whether any of the test scenarios developed during the NHTSA-NASA investigation could actually occur in real-world conditions.

“NASA found no evidence that a malfunction in electronics caused large unintended accelerations,” said Michael Kirsch, principal engineer at the NASA Engineering and Safety Center (NESC).

Nonetheless, NHTSA is considering taking several new actions as the result of the findings, including:

  • Propose rules, by the end of 2011, to require brake override systems, to standardise operation of keyless ignition systems, and to require the installation of event data recorders in all passenger vehicles
  • Begin broad research on the reliability and security of electronic control systems
  • Research the placement and design of accelerator and brake pedals, as well as driver usage of pedals, to determine whether design and placement can be improved to reduce pedal misapplication.

NHTSA and NASA will also brief the National Academy of Sciences panel currently conducting a broad review of unintended acceleration and electronic throttle control systems on the reports released today.

The NAS study was launched in spring 2010 alongside the NHTSA-NASA investigation and will be finalised later this year.

In 2009 and 2010, Toyota recalled nearly 8m vehicles as part of the sticky pedal – that extended beyond the US – and pedal entrapment recalls. Toyota also paid $48.8m in civil penalties as the result of NHTSA investigations into the timeliness of several safety recalls last year.

Timeline of Major Events (courtesy DoT/NHTSA)

  • March 29, 2007: NHTSA opens a preliminary investigation into pedal entrapment on MY’07 Lexus ES350 models based on five consumer complaints alleging three crashes and seven injuries. The all weather floor mat is identified as the possible cause of these incidents.
  • July 26, 2007: A fatal crash occurs in San Jose, CA involving a ‘07 Camry in which the driver suffers serious injuries and the driver of the struck vehicle is killed. The incident also appears to have been caused by a pedal trapped by an all weather floor mat.
  • September 13, 2007: After determining the fatal San Jose crash was caused by floor mat entrapment, NHTSA tells Toyota a recall is necessary.
  • September 26, 2007: Toyota recalls 55,000 floor mats in ’07 and ‘08 Camrys and ES350s.
  • August 28, 2009: A fatal crash occurs in Santee, CA, involving a loaner ’09 ES350. The vehicle is found to have an all weather floor mat from another Lexus vehicle. Investigators find that the vehicle’s previous driver had reported an entrapment incident to the dealership.
  • September 25, 2009: NHTSA meets with Toyota and tells the company that the floor mat recall is insufficient and the agency expects a recall for the defect in pedal design. Three days later, Toyota tells NHTSA the company will recall the gas pedals.
  • October 5, 2009: Toyota recalls 3.8m vehicles for pedal entrapment by floor mat and sends an interim letter to consumers telling them to remove floor mats. The defect remedy involves gas pedal reconfiguration, floor pan/carpeting revisions, and ‘brake pedal override’ software for vehicles with keyless ignition.
  • December 15, 2009: NHTSA officials meet with Toyota executives in Japan to explain NHTSA’s defect recall process and underscore Toyota’s obligations under U.S. law to find and report defects promptly. Toyota commits to making improvements.
  • January 16, 2010: Toyota informs NHTSA that certain CTS-brand pedals may have a dangerous ‘sticking’ defect. NHTSA calls an in-person meeting on January 19.
  • January 19, 2010: At the meeting, Toyota provides field reports on sticky pedal incidents, and NHTSA tells Toyota the agency expects prompt action.  Toyota informs NHTSA several hours later that the company will issue a recall.
  • January 21, 2010: Toyota recalls 2.3 million vehicles for the sticky pedal defect.
  • January 27, 2010: At NHTSA’s urging, Toyota expands its pedal entrapment recall to cover an additional 1.1 million vehicles.
  • February 16, 2010: NHTSA launches an official probe into the timeliness and scope of the pedal entrapment and sticky pedal Toyota recalls.
  • March 30, 2010: At the request of Congress, the U.S. DOT announces two studies into unintended acceleration. One looks at possible electronics causes for unintended acceleration in Toyotas; the other examines unintended acceleration and the safety of vehicle electronics across the automotive industry.
  • April 5, 2010: NHTSA demands the maximum, $16.375m, civil penalty on Toyota for its failure to notify the agency of the sticky pedal defect for more than four months after discovering it. Auto manufacturers are legally obligated to notify NHTSA within five business days of determining that a safety defect exists. Toyota pays the full fine on April 19.
  • December 20, 2010:Toyota agrees to pay the maximum $16.375m civil penalty as the result of another NHTSA investigation into whether their recall of 5.5mvehicles for pedal entrapment was conducted in a timely manner.