PRE-CRASH SAFETY SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Item Function
    Combination Meter Sub-assembly PCS Warning Light

    • Illuminates or flashes to warn the driver in accordance with signals from the driving support ECU assembly.

    • Flashes when the system is malfunctioning or temporarily disabled.

    • Illuminates when the pre-crash safety system is disabled using the pre-crash system switch.
    Multi-information Display Displays a warning message to inform or warn the driver of the system condition in accordance with signals from the driving support ECU assembly.
    Buzzer Sounds to warn the driver in accordance with signals from the driving support ECU assembly when the system is malfunctioning.
    Millimeter Wave Radar Sensor Assembly

    • Radiates millimeter wave radar forward, uses the reflected millimeter waves for detecting the presence of a vehicle ahead, the vehicle-to-vehicle distance, and the relative speed, and then transmits this information to the driving support ECU assembly.

    • Sounds the skid control buzzer assembly according to signals from the driving support ECU assembly.
    Driving Support ECU Assembly Makes judgments on whether a collision is possible based on the information received from the millimeter wave radar sensor assembly. It then outputs a seat belt operation signal and brake assist standby request signal and pre-crash brake request signal if required.
    Brake Booster Pump Assembly Receives an operation signal from the skid control ECU and generates hydraulic pressure for brake control.
    Brake Booster with Master Cylinder Assembly Master Cylinder Pressure Sensor Detects the master cylinder pressure and transmits a signal to the skid control ECU.
    Skid Control ECU

    • Receives a brake assist standby request signal from the driving support ECU assembly and switches the brake assist to standby mode. When a stop light switch signal is input, it activates the brake assist.

    • Receives a pre-crash brake request signal from the driving support ECU assembly, and then applies the brakes.

    • Transmits vehicle speed signals to the driving support ECU assembly.
    Stop Light Switch Stop Light Control Relay

    • Detects if the brake pedal is depressed and transmits a signal to the skid control ECU.

    • Receives a stop light turn on request signal from the skid control ECU, and turns on the stop lights.
    Speed Sensor (FR, FL, RR, RL) Detects the wheel speed of each of the 4 wheels and transmits the signals to the skid control ECU.
    Airbag ECU Assembly Yaw Rate Sensor Detects the yaw rate and lateral/longitudinal deceleration of the vehicle and transmits the signal to the skid control ECU and driving support ECU assembly.
    Spiral Cable with Sensor Sub-assembly Steering Angle Sensor Detects the angle and direction of steering and transmits a signal to the skid control ECU and the driving support ECU assembly.
    Pre-crash System Switch

    • Switches between the 3 warning timings (Far, Middle, and Near) when pressed.

    • Disables the pre-crash safety system when pressed and held.
    Skid Control Buzzer Assembly Sounds to warn the driver in accordance with signals from the millimeter wave radar sensor assembly.

  2. OPERATING CONDITION


    1. Operating Conditions

      Operating Conditions Pre-crash safety system operation has not been disabled using pre-crash system switch.

    2. The following pre-crash safety system controls are performed under the following conditions.

      Control Condition
      Pre-crash Safety System Warning

      • Vehicle speed is approximately 15 km/h (10 mph) or higher.


      • The relative speed of obstacle or vehicle ahead of is approximately 10 km/h (7 mph) or higher.


      • Pre-crash safety system operation has not been disabled using pre-crash system switch.
      Pre-crash Brake

      • Vehicle speed is approximately 15 km/h (10 mph) or higher.


      • The relative speed of obstacle or vehicle ahead is approximately 10 km/h (7 mph) or higher.


      • Pre-crash safety system operation has not been disabled using pre-crash system switch.
      Pre-crash Brake Assist

      • Vehicle speed is approximately 30 km/h (19 mph) or higher.


      • The relative speed of obstacle or vehicle ahead is approximately 30 km/h (19 mph) or higher.


      • Brake pedal is depressed.


      • Pre-crash safety system operation has not been disabled using pre-crash system switch.

  3. SYSTEM CONTROL


    1. High Possibility of Collision or Unavoidable Collision

      (1) The driving support ECU assembly determines that the possibility of a collision is high based on the signals received from the millimeter wave radar sensor assembly, steering angle sensor, speed sensor and yawrate sensor.
      (2) The driving support ECU assembly transmits a PCS warning display request signal to the combination meter sub-assembly and a skid control buzzer assembly request signal to the millimeter wave radar sensor assembly.
      (3) The driving support ECU assembly outputs a pre-crash brake assist request signal to the skid control ECU. Upon receiving this signal, the skid control ECU switches the brake assist to the standby condition. At this time, the skid control ECU activates pre-crash brake assist when the brake pedal is depressed by the driver.
      (4) The driving support ECU assembly determines that an unavoidable collision condition exists based on the signals received from the millimeter wave radar sensor assembly, speed sensor, steering angle sensor and yaw rate sensor.
      (5) The driving support ECU assembly outputs a pre-crash brake request signal to the skid control ECU.
      (6) The skid control ECU decreases the vehicle speed by activating the brake actuator to perform a pre-crash brake operation and activates the stop light control relay to turn on the stop lights.
      (7) If no collision occurs, the seat belts and brake assist will return to their normal states.
      A0050PHE05

  4. FUNCTION


    1. Warning displayed in combination meter sub-assembly


      1. The combination meter assembly uses the multi-information display, master warning light, PCS warning light and buzzer to provide the driver with pre-crash safety system warnings and indications.

      2. If the driving support ECU assembly determines that the possibility of a collision is high, it sends a signal to the combination meter assembly. Upon receiving this signal, the combination meter assembly indicates a warning using the multi-information display, PCS warning light and skid control buzzer assembly. Details are indicated below.

        When there is a high possibility of a collision
        Multi-information Display PCS OFF Indicator Light Skid Control Buzzer Assembly
        BRAKE ! Flashes Sounds Continuously

      3. When the system is not available, the following warning occurs to warn the driver.

        When a system malfunction is detected
        Multi-information Display Detail Master Warning Light PCS Warning Light Buzzer DTC

        PRE-CRASH SYSTEM

        MALFUNCTION VISIT YOUR DEALER

        		 This message appears when the driving support ECU assembly detects a system malfunction. Illuminates Flashes Sounds once Repair is required Corresponding DTCs are stored
        PRE-CRASH SYSTEM UNAVAILABLE

        This message appears when the driving support ECU assembly determines either of the following conditions is present:


        • Dirty millimeter wave radar sensor assembly

        • Poor weather conditions

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

        		 - Flashes - -
        When the pre-crash safety system has been disabled using the pre-crash system switch
        Multi-information Display Detail Master Warning Light PCS Warning Light Buzzer
        PRE-CRASH SYSTEM OFF

        • This message appears for 6 seconds on the multi-information display.

        • The pre-crash safety system has been disabled.

        		 - Illuminates -

  5. CONSTRUCTION


    1. Millimeter Wave Radar Sensor Assembly


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

      2. The millimeter wave radar outputs waves when the vehicle speed is above 2 km/h (1.24 mph), and not when the vehicle speed is at 0 km/h (0 mph). The millimeter wave radar uses frequencies in the 76 GHz band.

      3. The reception antennas receive the millimeter wave radar waves that have been reflected.

      4. The signal processing circuit detects the distance, relative speed, and the direction of the object by generating millimeter wave radar waves and calculating the signals received by the reception antennas. Then, it transmits this information to the driving support ECU assembly.

        A0050R8E03
        Text in Illustration
        *1 Millimeter Wave Radar Sensor Assembly - -
        *a Detection Distance: Approximately 150 m (490 ft.) *b Horizontal Angle: About 20°
        *c Vertical Angle: About 4° - -

      5. The distance to the object, azimuth and relative speed are calculated from the information that is provided by the reflection millimeter wave radar as described below.

        Item Calculation Method
        Distance Calculated from the length of time that has elapsed from the time the waves of the millimeter wave radar have been emitted, until the waves reflected by the millimeter wave radar are received. The detection distance is approximately 150 m (490 ft.).
        Azimuth Calculated from the angle of the waves reflected by the millimeter wave radar that have been received. The detection angle has a horizontal angle of about 20° and a vertical angle of about 8°.
        Relative Speed Calculated by utilizing the changes (Doppler effect*) that occur in the frequencies of the reflected millimeter wave radar waves.

        Tech Tips

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

        A0050ZXE34

        Tech Tips


        • Millimeter wave radar uses an extremely high frequency band between 30 GHz and 300 GHz, with an extremely short wavelength between 1 and 10 mm (0.04 to 0.40 in.) in a vacuum. The millimeter wave radar sensor of the pre-crash safety system uses frequencies in the 76.5 GHz band.

        • The millimeter wave radar is less affected by weather conditions such as rain, fog, or snow, and provides excellent characteristics for recognizing objects. Therefore, it is well suited to the pre-crash safety system and the dynamic radar cruise control system.

        • An SST is used if radar axis adjustment is needed. For details, refer to the Repair Manual.

        A0050QJE10

  6. OPERATION


    1. Pre-crash System Switch


      1. A pre-crash system switch is provided to disable the system. When pressed and held for approximately 3 seconds, the pre-crash safety system will be disabled. A message will be displayed for 6 seconds and the pre-crash system warning light will be illuminated. When the switch is pressed again while the system is disabled, the system will be reenabled.

      2. The switch is also used to change the warning timing in 3 levels: far, middle, near. The warning timing changes in the order below each time the switch is pressed.

    A0050NME02
    A00515J Pre-crash system switch is pressed briefly A0051E0 Pre-crash system switch is pressed and held for 3 seconds
    A0050XD Returns to previous screen when the switch is not operated for 6 seconds - -

  7. DIAGNOSIS


    1. Initial Check


      1. The driving support ECU assembly performs an initial check on the system for approximately 3 seconds after the power switch has been turned on (IG).

    2. Monitor Function


      1. After completing the initial check, the pre-crash safety system becomes ready to operate. During this time, the driving support ECU assembly periodically monitors the system for any malfunctions.

    3. Diagnostic Trouble Code (DTC)


      1. If the driving support ECU assembly detects a malfunction in the pre-crash safety system, it stores a 5 digit Diagnostic Trouble Code (DTC) in memory.