A federal study shows that Toyota Motor Corp.'s unintended acceleration problems were caused by mechanical issues, including a sticky pedal that Toyota blamed on a plastic part.
The study conducted by the U.S. Department of Transportation's National Highway Traffic Safety Administration and NASA engineers showed that the fault was not with the cars' electronic throttle control, said Transportation Secretary Ray LaHood in a Feb. 8 news conference.
“Our conclusions are this,” LaHood said: “Toyota's problems are mechanical, not electrical.”
Toyota City, Japan-based Toyota has recalled and repaired nearly 8 million cars because of problems with high-speed acceleration. It blamed the acceleration on two problems: a floor mat that entrapped the pedal, and a pedal that could get stuck or fail to release quickly.
Most vehicles, including Toyota's, use electronic throttle controls, but use springs and a friction device to give drivers a familiar feel to the pedal's movement. The pedals blamed in some of the issues had a metal spring and a plastic friction device within a pedal assembly supplied by CTS Corp. of Elkhart, Ind.
Toyota has used polyphenylene sulfide in models made since 2008 and nylon 4/6 in earlier models. Toyota said that the device sometimes was slow to return to normal, prompting some of the complaints.
During the recall, the company placed a specially designed steel reinforcement bar between two plastic surfaces to reduce excess friction.
Congress and some industry watchers questioned if the problem could solely be blamed on the pedal, or whether electronic throttle controls could have a glitch that caused the acceleration.
Those questions prompted the NHTSA and NASA study as well as a second study, which is still continuing, by the National Academy of Sciences.
Federal officials also said they will improve their understanding and research into electronic controls to ensure the agencies can more closely track the growing range of electronic control systems used on passenger vehicles. In addition, NHTSA will launch a study into pedal placements to help eliminate driver confusion between accelerator and brake pedals while they are driving, officials said.