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System Description

WARNING: This page is about a different car, the 2010 Lexus GS 450h. However, it is still accessible from the selected car via links, so may be relevant.
  1. PRE-COLLISION SYSTEM DESCRIPTION 
    1. The pre-collision system optimizes and activates occupant protection equipment (see below) to attempt to reduce damage from collisions.
  2. OUTLINE OF PRE-COLLISION SYSTEM 
    Operating Condition Control Transmitting ECU Receiving ECU Part operated
    Operates according to sensor detection Pre-collision seat belts Distance control ECU Seat belt control ECU Front seat outer belts
    Operates according to sensor detection Pre-collision brake assist Distance control ECU Skid control ECU Brake assist system
    Operates according to sensor detection Damping force control Distance control ECU Absorber control ECU Shock absorbers
    Operates when sudden braking occurs Pre-collision seat belts Skid control ECU Seat belt control ECU Front seat outer belts
    Operates according to sensor detection Pre-collision brake Distance control ECU Skid control ECU Brake system
    1. When operating according to sensor detection:

      The pre-collision sensor (millimeter wave radar sensor) detects vehicles and other objects on the road in front of the user's vehicle. The distance control ECU determines if a collision is unavoidable based on object position, speed and track information. If the distance control ECU determines that a collision is unavoidable, it transmits this information to the following areas through 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 (initiates control of pre-collision brake system)
      • Absorber control ECU (tightens the suspension as much as possible)
    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 or lose control of the vehicle. If so, the skid control ECU sends a signal to the seat belt control ECU through the CAN communication and the pre-collision seat belt activates.

  3. OUTLINE OF PRE-COLLISION SEAT BELT CONTROL 
    1. The pre-collision seat belt operates depending on what the sensor detects, or whether or not sudden braking has occurred or lose control of the vehicle. The pre-collision seat belt motor tightens the seat belt to help improve occupant protection 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 SYSTEM 
    1. The pre-collision brake assist system 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 vehicle speed reduction rate.
    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 distance control 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 distance control ECU determines that a collision is unavoidable:

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

  5. OUTLINE OF PRE-COLLISION BRAKE CONTROL 
    1. The pre-collision brake 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 blinks.

    2. Operative condition
      1. Refer to the sensor description under "Outline of Pre-Collision Safety System" (see above).
      2. When the distance control ECU determines that a collision 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 Brake*2
    Power switch off or on (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: Operates according to brake operation.
    • *2: Operates according to sensor detection.
    • *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 distance control ECU may determine that a collision is unavoidable, and activate the pre-collision system. However, this is not abnormal.
      Fig 1: Identifying Precaution For Pre-Collision System Operation
      GTY256159Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT: 

      • The pre-collision system will 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
        Objects that cannot be detected Plastic items (safety cones)
        Objects that cannot be detected in a stable manner People, bicycles, motorcycles, trees, animals, snow fence, etc.
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