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System Description [12/2015 - 11/2017]

  1. PRE-COLLISION SYSTEM 
    1. The pre-collision system optimizes and activates occupant protection equipment (see below) to attempt to reduce damage due to a collision.
  2. OUTLINE OF PRE-COLLISION SYSTEM 
    Operating Condition Control Transmitting ECU Receiving ECU Part Operated
    Operates according to sensor detection Pre-collision alarm Driving Support ECU Assembly
    • Combination meter assembly (warning message)
    • Skid control ECU (warning buzzer)
    • Combination meter assembly (warning message)
    • Skid control buzzer assembly (warning buzzer)
    Operates according to sensor detection Pre-collision seat belt Driving support ECU Seat belt control ECU Front seat outer belts
    Operates according to sensor detection Pre-collision brake assist Driving support ECU Skid control ECU Brake assist system
    Operates when sudden braking occurs Pre-collision seat belt Skid control ECU Seat belt control ECU Front seat outer belts
    Operates according to sensor detection Pre-collision braking Driving support ECU Skid control ECU Brake system
    1. When operating according to sensor detection:

      The millimeter wave radar sensor detects vehicles and other objects on the road in front of the user's vehicle. The driving support ECU determines if a collision is unavoidable based on object position, speed and track information. If the driving support ECU determines that a collision is unavoidable, it transmits this information to the following areas using CAN communication:

      • Seat belt control ECU (initiates control of pre-collision seat belts)
      • Skid control ECU (activates pre-collision brake assist system)
      • Skid control ECU (activates pre-collision braking)
    2. When operating as a result of sudden braking:

      The skid control ECU uses brake pressure information and other data to determine if the driver has suddenly applied the brakes. (Even when a judgment has been made that the vehicle is out of control, the skid control ECU continues to output operation commands.) If so, the skid control ECU sends a signal to the seat belt control ECU through CAN communication and the pre-collision seat belts activate.

  3. OUTLINE OF PRE-COLLISION SEAT BELT CONTROL 
    1. The pre-collision seat belts operate depending on what the sensor detects, or whether sudden braking has occurred. (Even when a judgment has been made that the vehicle is out of control, the skid control ECU continues to output operation commands.) The pre-collision seat belt motor tightens the seat belt to optimize occupant restraint performance.
    2. Operative condition
      1. Refer to the sensor and sudden braking descriptions under "Outline of Pre-Collision System" (see above).
  4. OUTLINE OF PRE-COLLISION BRAKE ASSIST CONTROL 
    1. The pre-collision brake assist operates depending on what the sensor detects. The system then enters standby mode before a collision. When the driver depresses the brake pedal, brake fluid pressure is increased to improve fluid pressure response and improve the rate of deceleration.
    2. Operative condition
      1. Refer to the sensor description under "Outline of Pre-Collision System" (see above).
      2. When the driver depresses the brake pedal after the driving support ECU determines that a collision is unavoidable:

        Brake fluid pressure is increased at the same time the driver depresses the brake pedal.

      3. When the driver depresses the brake pedal before the driving support ECU determines that a collision is unavoidable:

        Brake fluid pressure is increased at the same time that the driving support ECU receives a pre-collision sensor signal (indicating that other vehicles or objects are in front of the vehicle).

  5. OUTLINE OF PRE-COLLISION BRAKING CONTROL 
    1. The pre-collision braking operates depending on what the sensor detects. This system can be canceled by the pre-collision brake cancel switch.

      HINT: 

      While the pre-collision brake is canceled, the PCS indicator light on the combination meter turns on.

    2. Operative condition
      1. Refer to the sensor description under "Outline of Pre-Collision System" (see above).
      2. When the driving support ECU determines that a crash is unavoidable, the system performs brake control to reduce the vehicle speed.
  6. OPERATIVE CONDITION AND INOPERATIVE CONDITION OF EACH CONTROL (REVIEW) 
      Pre-Collision Seat Belt*1 Pre-Collision Seat Belt*2 Pre-Collision Brake Assist*2 Pre-Collision Braking*2
    Ignition switch off or ACC - - - -
    When a warning message is displayed on the multi-information display *3 *3 *3 *3
    When seat belt(s) is/are fastened *4 *4 ◦ ◦
    Operates when the vehicle speed is 30 km/h (18 mph) or more, regardless of relative speed ◦ - - -
    Operates when the vehicle speed is 5 km/h (3 mph) or more and relative speed is 30 km/h (18 mph) - ◦ - -
    Operates when the vehicle speed is 15 km/h (9 mph) or more and relative speed is 15 km/h (9 mph) - - - ◦
    Operates when the vehicle speed is 30 km/h (18 mph) or more and relative speed is 30 km/h (18 mph) - - ◦ -
    When the vehicle collides with an object outside the detection range of the millimeter wave radar sensor (side crash, rear crash, etc.) ◦ - - -
    When the millimeter wave radar sensor cannot detect a possible crash object ◦ - - -
    • *1: During emergency braking, or when the vehicle is judged to be out of control. (During emergency braking.)
    • *2: Operates according to sensor detection. (When a collision is imminent.)
    • *3: Inoperative parts are different depending on malfunction areas.
    • *4: Only operates when seat belt is fastened.
    • ◦: Main basis for operation
    • -: Does not operate, or not main basis for operation
  7. PRECAUTION FOR PRE-COLLISION SYSTEM OPERATION 
    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 activate the pre-collision system. This activation of the system is not abnormal.
      Fig 1: Pre-Collision System Operation Conditions
      GTY464767Courtesy 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 left turn. *d Crossing a narrow metal bridge.
      *e There are metal objects on the road. *f Approaching a leading vehicle suddenly.
      *g Approaching an electrical toll collection gate (reacts 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 sensor (reinstallation, collision, etc).
      *k There is a billboard or sign at the top of an incline. *l There are metal objects at the bottom of a decline (a metal plate covering road construction, a mesh drain cover, a manhole, etc.).
      *m Roughness in road surface. *n When passing through a tunnel

      HINT: 

      • The pre-collision system will not activate when approaching safety cones or other plastic objects as they cannot be detected by the pre-collision sensor.
      • 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
        Objects that cannot be detected Plastic items (safety cones)
        Objects that cannot be detected in a stable manner People, bicycles, motorcycles, trees, animals, snow fences, etc.
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