System Description [09/2014 - 10/2015]

1. The pre-collision system detects vehicles and obstacles in front of the vehicle and performs the following: 1) optimally uses system controls to avoid collisions, and 2) uses system controls to reduce impact during a collision.

1. Front collision detection
   1. The driving support ECU receives information about vehicles and obstacles in front of the vehicle from the millimeter wave radar sensor assembly. Then, based on vehicle speed, road conditions and obstacle location, the driving support ECU determines, in advance, the risk of a crash and if a crash is unavoidable.
   2. The driver monitor camera detects the direction that the driver's head is facing and whether the driver's eyes are open or closed. When a potential crash is detected and the camera determines that the driver's head is not facing forward or that the driver's eyes are closed, it activates the pre-collision safety controls in advance.
2. Sudden braking detection
   1. The skid control ECU assembly activates the pre-collision seat belts when it detects sudden braking. Sudden braking is determined based on brake oil pressure and other information from the master cylinder pressure sensor.
3. Vehicle control impossible judgment
   1. The pre-collision seat belts are activated when it is determined that the vehicle cannot be controlled. The judgment is based on vehicle stability information from the yaw rate sensor and steering angle sensor.
4. Component

   Component	Detection Content
   Millimeter wave radar sensor assembly	Front object
   Skid control ECU assembly	Sudden braking or vehicle control is not possible
   Driver monitor camera	Driver facial direction Driver eye opening level signal

1. When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, the multi-information display and warning buzzer are used to warn the driver and help with collision avoidance.

1. When the system determines that a collision with an obstacle is unavoidable, that sudden braking has occurred, or that vehicle control is impossible, the system performs seat belt control. During seat belt control, slack in the seat belts is reduced to increase occupant restraint and aid the pretensioner.

1. When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, brake assist is set to standby mode. Then, when the driver depresses the brake pedal, the hydraulic brake pressure is increased to improve braking effectiveness.

1. When it is determined that there is a risk of colliding with an obstacle in front of the vehicle, the AVS is operated to control the damping force, suppress nose diving and rolling, and support collision avoidance through steering.

1. When the system determines that a collision with an obstacle is unavoidable, the system performs brake control to reduce the vehicle speed. The pre-collision brake response time in cases when there is a vehicle in front has been increased. This results in less damage and injury.

1. When the pre-collision system cancel switch assembly in the No. 1 instrument panel under cover sub-assembly is turned on, the pre-collision system does not operate.

   HINT: 

   While the pre-collision system cancel switch is ON, the combination meter's PCS indicator light blinks.

HINT: 

• ◦: Operation
• X: Not operation
• *1: Inoperative parts are different depending on malfunction areas
• *2: Only operates when seat belt is fastened
• *3: Pre-collision seat belts may operate

1. When the millimeter wave radar sensor detects an object in front of the vehicle under the conditions described below, the driving support ECU may determine that a collision is unavoidable, and activates the pre-collision system. However, this is not abnormal.
   Fig 1: Identifying Conditions That May Activate Pre-Collision System

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

   *a	There are objects on the side of the road at the beginning of a curve (a guardrail, street lamp, billboard, etc.).	*b	Passing an oncoming vehicle on a curve.
   *c	There is an oncoming vehicle when making a right turn.	*d	Crossing a narrow metal bridge.
   *e	There are metal objects on the road.	*f	Approaching leading vehicle suddenly.
   *g	Electrical Toll Collection gate. (React to bar.)	*h	Crossing an overpass, traffic sign, signboard
   *i	The vehicle height drastically changes (nose-up, nose-down).	*j	Misalignment of millimeter wave radar occurs. (re-install, collision, etc)
   *k	There are metal objects at the bottom of a decline (a metal plate covering road construction, a mesh drain cover, a manhole, etc.)	*l	There is a billboard or sign at the top of an incline.
   *m	Roughness on road surface.	-	-

   HINT: 

   • The pre-collision system does not activate when the pre-collision sensor detects safety cones and other plastic objects.
   • The pre-collision system may or may not activate when the pre-collision sensor detects the following objects: people, bicycles, motorcycles, trees, animals and snow fences.

   Object Type	Example
   Object that cannot be detected	Plastic items (safety cones)
   Object that cannot always be detected	People, bicycles, motorcycles, trees, animals, snow fences, etc.