Dealer Letter: The Pre-Collision System (PCS) uses a radar sensor to determine the possibility of a frontal collision. FCC regulations require the radar sensor to be temporarily inactive while the vehicle is stopped. Due to a program error in the Driving Support ECU, if the radar sensor is inactive for 10 seconds or more, the PCS may not reactivate on certain 2011-2014 Model Year Sienna vehicles equipped with PCS.