While driving on a limited access highway at highway speed, the passenger bumped the transmission shift control with his leg, moving the vehicle from automatic mode into manual mode, causing the vehicle to shift into 3rd gear, and causing a corresponding abrupt slowdown of the vehicle without actuation of the brake lights to warn following vehicle of the slowdown. A following vehicle had to brake hard to avoid a collision with my Scion Xb, while I corrected the situation by shifting the transmission control back into automatic mode. I believe there is an insufficient detente mechanism to retain the vehicle in automatic transmission mode, and that accidental shifts into manual mode at highway speeds are not adequately prevented. An unintended downshift caused by a passenger could result in an accident causing great injury if it were to occur in heavy traffic at highway speeds. The vehicle could also be damaged by these unintended/uncommanded downshifts, causing a catastrophic failure of the vehicle during subsequent Excursion.

- Holly Springs, GA, USA