PRE-CRASH SAFETY SYSTEM (RADAR TYPE)


  1. General

    Item Function
    Combination Meter Assembly PCS Warning Light Illuminates or flashes to warn the driver in accordance with signals from the seat belt control ECU.
    Multi-information Display Displays a warning message to inform or warn the driver of the system condition in accordance with signals from the seat belt control ECU.
    Master Warning Light Illuminates to warn the driver in accordance with signals from the seat belt control ECU.
    Multi Buzzer Sounds to warn the driver in accordance with signals from the seat belt control ECU.
    Millimeter Wave Radar Sensor Radiates millimeter waves forward, uses the reflected millimeter waves for detecting the presence of a vehicle being driven ahead, the vehicle-to-vehicle distance and the relative speed, and transmits these pieces of information to the distance control ECU.
    Front Seat Outer Belt Seat Belt Motor Retracts the seat belt in accordance with signals received from the seat belt control ECU.
    Front Seat Inner Belt Seat Belt Buckle Switch

    • Detects the condition (verifies use of belt) of the driver seat belt and transmits a signal to the airbag sensor assembly.

    • Detects the condition (verifies use of belt) of the front passenger seat belt and transmits a signal to the seat belt control ECU.
    Airbag Sensor Assembly Transmits the condition (fastened or unfastened) of the driver seat belt to the seat belt control ECU.
    Distance Control ECU Makes a judgment that a collision is unavoidable based on the information received from the millimeter wave radar sensor. The ECU then outputs a seat belt operation signal and brake assist standby request signal.
    Seat Belt Control ECU

    • Receives a seat belt operation request signal from the distance control ECU or skid control ECU and operates the seat belts.

    • If the seat belt control ECU detects a malfunction in the pre-crash safety system, it will store Diagnostic Trouble Code (DTC).
    Skid Control ECU

    • Receives a brake assist standby request signal from the distance control ECU and switches the brake assist to the standby mode. When a stop light switch signal is input, the ECU operates the brake assist.

    • Determines that the brakes have been applied suddenly through a signal received from the master cylinder pressure sensor, and outputs a seat belt operation signal to the seat belt control ECU.

    • Determines the presence of a front wheel skid tendency or rear wheel skid tendency, and outputs a seat belt operation signal to the seat belt control ECU.

    • Transmits a vehicle speed signal to the distance control ECU.
    Wheel Cylinder Pressure Sensor Detects the wheel cylinder pressure and transmits a signal to the skid control ECU.
    Brake Actuator Master Cylinder Pressure Sensor Detects the master cylinder pressure and transmits a signal to the skid control ECU.
    Pump Motor Receives an actuation signal from the skid control ECU and generates hydraulic pressure for brake control.
    Stop Light Switch Detects if the brake pedal is pressed and transmits a signal to the skid control ECU.
    Vehicle Speed Sensor Detects the wheel speed signal and transmits a signal to the skid control ECU.
    Yaw Rate and Deceleration Sensor Detects the yaw rate and lateral/longitude deceleration of the vehicle and transmits a signal to the skid control ECU and the distance control ECU.
    Steering Angle Sensor Detects the angle and direction of steering and transmits a signal to the skid control ECU and the distance control ECU.

    Tech Tips

    When the seat belt control ECU is replaced, an active test of the seat belt motor must be performed in accordance with the following procedure to check that the motor operates properly:


    1. Turn the engine switch on (IG).

    2. Monitor the PCS warning light for at least 3 seconds after the engine switch is turned on (IG). Make sure that the warning light does not remain on.

    3. Connect the Global TechStream (GTS) to the DLC3 and enter the select active test mode.

    4. Perform an active test of the seat belt motor and check that the motor operates properly.

    For details, refer to the Repair Manual.

  2. Combination Meter Assembly


    1. The combination meter assembly is provided with the master warning light, PCS warning light, buzzer and multi-information display to inform the driver of a malfunction in the pre-crash safety system.

    2. 2 types of warning messages are used for the pre-crash safety system as described below. The pre-crash safety system will not operate when these messages appear in the combination meter assembly.

      Warning Message Detail Master Warning Light PCS Warning Light Multi Buzzer DTC
      CHECK PCS SYSTEM This message appears when the seat belt control ECU detects a system malfunction. Illuminates Illuminates Sounds Once ○
      PCS TEMPORARILY NOT AVAILABLE

      This message appears when the seat belt control ECU determines the following conditions:


      • Dirty millimeter wave radar sensor*

      • Poor weather condition

      • Overheated seat belt control ECU.

      After these conditions have been eliminated, the system will operate normally.

      		 - Flashes - ●

      ○: Repair is required/DTC is output

      ●: Repair is not required/DTC is not output

      -: Not available

      *: When the vehicle is driving on a road with less traffic and less objects to reflect millimeter waves, the distance control ECU may determine it as a dirty millimeter wave radar sensor condition because the millimeter wave radar sensor can not detect any reflected millimeter waves. After that, however, once the millimeter wave radar sensor detects reflected millimeter waves, the pre-crash safety system will resume automatically.

  3. Millimeter Wave Radar Sensor


    1. General


      1. The millimeter wave radar sensor consists of a millimeter wave radar circuit, signal processing circuit and CPU.

      2. The millimeter wave radar circuit consists of transmission antenna and reception antennas.

      3. The millimeter wave radar sensor outputs millimeter waves when the vehicle speed is above 0 km/h (0 mph), and does not when the vehicle speed is at 0 km/h (0 mph). The millimeter wave radar sensor uses frequencies in the 76 GHz band.

      4. The reception antennas receive the millimeter waves that have been reflected.

      5. The signal processing circuit detects the distance, relative speed and direction of the object by generating millimeter waves and calculating the signals received by the reception antennas. Then, it transmits this information to the distance control ECU.

      6. The millimeter wave radar sensor is also used by the dynamic radar cruise control system.

        A01W5UMC01
        *a Millimeter Wave Radar Circuit *b Signal Processing Circuit
        *c Image Diagram *d Vertical Angle: Approx. 8°
        *e Detection Distance: Approx. 150 m (492 ft.) *f Horizontal Angle: Approx. 20°

    2. Calculation Method


      1. The distance to the object, azimuth (horizontal angle), and relative speed are calculated from the information that is provided by reflected millimeter waves as described below.

        Distance Calculated based on the length of time between emission and reception of millimeter waves by the millimeter wave radar sensor.
        Azimuth Calculated based on the angle of the millimeter wave reflected by an object.
        Relative Speed Calculated by utilizing the changes (Doppler effect*) that occur in the frequencies of the reflected millimeter waves.

        *: The Doppler effect causes the observer to perceive the radio waves emitted by a moving object to be at higher frequencies as it approaches, and to be at lower frequencies as it recedes. This phenomenon is created because when an object is located far away, the radio waves are perceived at higher frequencies than when it is at the radio source.

        A01W6AIE09