Page 126 - Toyota Under Fire

THE RECALL CRISIS

The Saga of the Sticky Pedals

Among the many challenges of switching from mechanical to
electronic systems is re-creating the feel of a mechanical system.
Since so much of driving is habitual behavior—we manage to
control our vehicles without a great deal of conscious thought
and attention—it’s very important for the driving experience, in-
cluding the way the pedals feel, to remain constant. In a me-
chanical throttle mechanism, it requires force to push down the
pedal to pull the cable that opens the throttle—and there’s force
pushing the pedal back to idle as a driver removes her foot. An
electronic throttle control system has to re-create these sensations
(even though technically they are not necessary) so that the driv-
ing experience doesn’t materially change.
To do so requires designing pedal assemblies that require an
amount of force roughly equal to the amount required to depress
a pedal mechanically connected to the throttle and that push
back after you remove your foot; this is achieved with a mix of
springs, pivots, and dampers. The dampers’ role is to provide the
right amount of friction so that the pedal moves smoothly, both
when it is being depressed and when it is returning to the idle po-
sition. Historically, Denso, one of the original Toyota suppliers
in Japan, was Toyota’s main supplier of pedals, but over the years
Toyota has localized the supply of many parts. In the 2005 model
year, Toyota began using CTS as a supplier for pedals; the CTS
pedals eventually became standard in most North American and
some European vehicles.
During the course of 2008, Toyota’s European operations
had investigated four vehicles where drivers had reported that the
accelerator was slow to return or was sticking in a partially open

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