The headline for the NHTSA/NASA report on the Toyota unintended acceleration, as widely reported, was that Toyota's electronics were not at fault, because the overwhelming evidence was that people were either pressing the wrong pedal, or the pedal was entrapped/stuck.
Vehicle testing using a defective potentiometer accelerator pedal assembly from a VOQ vehicle with a resistive short, within a narrow range of values between the sensors outputs, identified a vulnerability that may compromise nominal limp home mode fail-safe operation on subsequent ignition key cycles and affect the malfunction indicator lamp (MIL) display and/or DTC generation under certain specific conditions. Destructive physical analysis of this pedal assembly found tin whiskers, one of which had formed the resistive partial short circuit between the pedal signal outputs. A second tin whisker of similar length was also found in this pedal assembly that had not caused an electrical short. If a resistive short between the potentiometer accelerator pedal signal outputs exists, the system may be vulnerable to a specific second fault condition that could theoretically lead to UA.However, if resistive faults were occurring during normal use, DTCs would be expected from at least the first ignition key cycle and the following cycles that did not meet the specific criteria. Subsequent review of the warranty data does not support an observable failure signature of pedal-induced DTCs. Electrical measurements on six VOQ vehicles found no indication of the resistive paths necessary for this failure scenario.