The shim is smaller than the size of a quarter, and it's designed to release tension in the pedals, said Joel Goldschmitt, a technical specialist with Toyota.
The shim "goes in and releases some of that tension and prevents that friction shoe from wearing in the future, so it will last a long time," said Goldschmitt.
The repair is expected to take two hours per vehicle, said Steve Zion, of the Connecticut Toyota Dealers Association.
"Toyota is so on this that they want everybody schooled by the engineering department and they're bringing them all in to train and no other manufacturer's ever done that," said Zion.
The auto mechanics also received training on Toyota's other problem of floor mats sticking under the gas pedal on some models.
Dealers are prepared to fix both problems at the same time, if needed.