Design Con 2015

Toyota accelerations revisited—hanging by a (tin) whisker

Rick Demeis, EE Times -January 10, 2012

Several accelerator pedal position sensors had tin whiskers that could cause short circuits. A NASA paper delivered at the International Tin Whisker Symposium last year reported on tin whisker growth in Toyota accelerator pedal position sensors that, depending on pedal rate of movement, could lead to unintended acceleration.

The whiskers were found in a "failed" sensor from a 2003 Camry and at least two other similar units that did not malfunction. The sensor in question was used on the Camry from 2002 to 2006 model years, and the specific Camry with the defective sensor (which was furnished to NASA) had 82,000 miles on it. The vehicle owner reported the car as "undrivable," with throttle response as: "I couldn't get any 'gas', and then the car would jerk forward at a rapid rate." The sensor had at least 17 whiskers in it, only one of which shorted contacts.


While the inspected sensors noted above could be typical of the entire lot, these incidents of whisker growth and shorting give cause for safety concern across the industry.

The NASA paper gives further insight by detailing tin whisker physical behavior as well as outlining guidelines and methods of detecting whiskers. But rather than summarize the report here, readers can access the easily-read, but complete, 30-page NASA presentation by clicking here.

This story was originally posted by EE Times.

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