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
Rick DeMeis is editor of Automotive Designline.