System Description [08/2015 - 08/2019]

1. The pre-collision system detects vehicles and obstacles in front of the vehicle and performs the following: 1) the system uses the multi-information display and sounds a buzzer to warn the driver of a collision and prompt preventive action, 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 and lane recognition camera sensor assembly*. Then, based on vehicle speed, road conditions and obstacle location, the driving support ECU determines in advance the possibility of a collision and if a collision is unavoidable.
      1. *: w/ Lane Departure Alert System
   2. w/ Driver Monitor Camera:

      The driver monitor camera detects the direction that the driver's head is facing. When a potential collision is detected and the camera determines that the driver's head is not facing forward, the driver monitor ECU activates the pre-collision controls in advance. If the possibility of a collision increases and the driver's head is still not facing forward, warning brake control operates.

2. Sudden braking detection
   1. The skid control ECU 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 there is a high probability 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
   Lane recognition camera sensor assembly*1	Front object
   Driver monitor camera*2	Driver facial direction

   1. *1: w/ Lane Departure Alert System
   2. *2: w/ Driver Monitor Camera

1. *: w/ Air Suspension

1. When the system determines that there is a possibility of a collision 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.
2. w/ Driver Monitor Camera:
   • When the system determines that there is a possibility of a collision with an obstacle in front of the vehicle, the system warns the driver to help prevent a collision by displaying messages in the multi-information display in the combination meter assembly, sounding the buzzer and illuminating the PCS indicator light.
   • When the system determines that there is a possibility of a collision and the driver monitor camera detects that the driver's head is not facing forward for a specified period of time, the warnings are performed earlier than normal.

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 aid the pretensioner.

1. When the system determines that there is a possibility 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 possibility 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.

1. When the pre-collision brake cancel switch assembly in the No. 1 instrument panel under cover sub-assembly is turned on, the pre-collision alarm and pre-collision brake do not operate.

   HINT: 

   While the pre-collision brake cancel switch assembly is on, the PCS indicator light in the combination meter assembly illuminates.

HINT: 

• ◦: Operates
• X: Does not operate
• *1: Inoperative functions are different depending on malfunction areas
• *2: Operates regardless of whether the seat belts are fastened or not
• *3: Pre-collision seat belts may operate when brakes are suddenly applied
• *4: w/ Air Suspension
• *5: w/ Driver Monitor Camera

1. *: w/ Lane Departure Alert System

1. When the millimeter wave radar sensor assembly and lane recognition camera sensor* detect an object in front of the vehicle under the conditions described below, the driving support ECU may determine that a collision is unavoidable and activate the pre-collision system. However, this is not abnormal.
   Fig 1: Millimeter Wave Radar Sensor Detection Examples

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT: 

   • The pre-collision system is not activated by safety cones and other plastic objects which cannot be detected by the millimeter wave radar sensor assembly and lane recognition camera sensor assembly*.
   • The pre-collision system may or may not be activated by the following objects which cannot always be detected by the millimeter wave radar sensor assembly and lane recognition camera sensor assembly*: people, bicycles, motorcycles, trees, animals, snow fences, etc.

   Object Type	Example
   Object that cannot be detected	Safety cones, plastic items
   Object that cannot always be detected	People, bicycles, motorcycles, trees, animals, snow fences, etc.