LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2009 >> LS 600hL >> Repair and Diagnosis >> External Pages >> Different car >> Section 43 (Pre-Collision) >> Pre-Collision System >> System Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

System Description

WARNING: This page is about a different car, the 2008 Lexus LS 600hL. 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 detects vehicles and obstacles in front of the vehicle and performs the following-1) optimally uses system controls to avoid crashes, and 2) uses system controls to reduce impact during a crash.
  2. PRE-COLLISION DETECTION OUTLINE 
    1. Front collision detection
      1. The driving support ECU receives information about vehicles and obstacles in front of the vehicle from the front millimeter wave radar sensor and object recognition camera. 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. When a potential crash is detected and the camera determines that the driver's head is not facing forward, it activates the pre-collision controls in advance.
    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 CHART

    Component Detection Content
    Front millimeter wave radar sensor Front object
    Object recognition camera Front object
    Driver monitor camera Driver facial direction
  3. PRE-COLLISION SYSTEM CONTROL DESCRIPTION 
    PRE-COLLISION SYSTEM CONTROL DESCRIPTION CHART

    Operation Condition Controls Sender ECU Receiver ECU Part Operated
    Front crash detection
    1. Crash is possible
    		 Pre-collision alarm Driving support ECU
    • Combination meter
    • Skid control ECU
    • Combination meter
    • Skid control buzzer
    1. Crash is unavoidable
    		 Pre-collision seat belts Driving support ECU Seat belt control ECU Front seat outer belts
    1. Crash is possible
    2. Crash is unavoidable
    		 Pre-collision brake assist Driving support ECU Skid control ECU Brake assist system
    1. Crash is possible
    2. Crash is unavoidable
    		 Pre-collision brake Driving support ECU Skid control ECU Brake assist system
    1. Crash is possible
    2. Crash is unavoidable
    		 Air suspension control Driving support ECU Suspension control ECU Shock absorber
    1. Crash is possible
    		 Variable gear ratio steering control Driving support ECU Steering control ECU Steering actuator
    Sudden braking detected Pre-collision seat belts Skid control ECU Seat belt control ECU Front seat outer belts
    Vehicle control impossible judgment Pre-collision seat belts Skid control ECU Seat belt control ECU Front seat outer belts
  4. PRE-COLLISION ALARM CONTROL 
    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 crash avoidance.
  5. PRE-COLLISION SEAT BELT CONTROL 
    1. When the system determines that a crash 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.
  6. PRE-COLLISION BRAKE ASSIST CONTROL 
    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.
  7. AIR SUSPENSION CONTROL 
    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
  8. VARIABLE GEAR RATIO STEERING CONTROL 
    1. When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, the Variable Gear Ratio Steering (VGRS) system is set to standby at an optimum steering ratio (i.e., increasing power steering) for collision avoidance.
  9. PRE-COLLISION BRAKE CONTROL 
    1. When the system determines that a crash with an obstacle is unavoidable, the system performs brake control to reduce the vehicle speed.
  10. PRE-COLLISION BRAKE CANCEL SWITCH 
    1. When the pre-collision brake cancel switch in the glove box is turned ON, the pre-collision alarm and pre-collision brake do not operate.

    HINT:

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

  11. PRE-COLLISION SYSTEM OPERATING CONDITION 
    PRE-COLLISION SYSTEM OPERATING CONDITION CHART

    Vehicle Condition Pre-collision Alarm Pre-collision Seat Belt*1 (Linked with Vehicle Tilt and Sudden Brake Operation) Pre-collision Seat Belt*2 (Linked with Radar) Pre-collision Brake Assist Pre-collision Brake Air Suspension Control Variable Gear Ratio Steering Control
    Power switch OFF or ON (ACC) X X X X X X X
    When warning message is displayed on multi-information display *1 *1 *1 *1 *1 *1 *1
    When seat belt (s) are fastened O *2 *2 O O O O
    When own vehicle speed is 30km/h (18 mph) or more, regardless of relative speed X O X X X X X
    When own vehicle speed is 15km/h (9 mph) or more and relative speed is 20 km/h (12mph) X X X X O X X
    When own vehicle speed is 5 km/h (3 mph) or more and relative speed is 30 km/h (18 mph) X X O X X O O
    When vehicle collides with object outside detection range of front millimeter wave radar sensor (side collision, etc) X *3 X X X X X
    When front millimeter wave radar sensor cannot detect possible collision object X *3 X X X X X
    When own vehicle speed is 30 km/h (18 mph) or more, and relative speed of other vehicle is 30 km/h (18 mph) or more X X X O X X X
    Pre-collision brake cancel switch ON X O O O X O O
    HINT
    • O: Operation
    • X: No 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 when brakes are suddenly applied
  12. PRECAUTION FOR FRONT MILLIMETER WAVE RADAR SENSOR AND OBJECT RECOGNITION CAMERA 
    1. When the front millimeter wave radar sensor and object recognition camera 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 activates the pre-collision system. However, this is not abnormal.
    Fig 1: Precaution For Front Millimeter Wave Radar Sensor And Object Recognition Camera
    G04950858Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    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 CHART

    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
scientia non olet · About LEMON Manuals