LEXUS PARKING ASSIST-SENSOR SYSTEM SYSTEM DESCRIPTION


  1. GENERAL


    1. This system uses ultrasonic sensors to detect any obstacles at the corners and the rear of the vehicle. The system then informs the driver of the distance between the sensors and an obstacle as well as their positions by indicating them on the multi-information display (in the combination meter) and multi-display (w/ Navigation System) and by sounding a buzzer.

  2. FUNCTION OF COMPONENTS

    Component Function
    Ultrasonic Sensor (6) Detects the distance between the vehicle and an obstacle
    No. 1 Clearance Warning Buzzer

    • Sounds for 1 second to inform the driver when the LEXUS parking assist-sensor system power is turned on (the power switch is on (IG) and the LEXUS parking assist-sensor system is on)*1

    • Sounds to inform the driver according to the distance to an obstacle
    Multi-information Display on Combination Meter Assembly

    • Displays the location of an obstacle and the approximate distance between the vehicle and the obstacle

    • Displays a malfunction of the ultrasonic sensor to inform the driver
    Clearance Sonar Indicator on Combination Meter Assembly Illuminates to inform the driver while the LEXUS parking assist-sensor system power is on (the power switch is on (IG) and the LEXUS parking assist-sensor system is on)
    Combination Meter Assembly Transmits the vehicle speed signal to the clearance warning ECU assembly*5 or parking assist ECU*4
    Back Sonar or Clearance Sonar Switch Assembly Operating this switch enables, disables or cuts off the operation of the LEXUS parking assist-sensor system
    Clearance Warning ECU Assembly

    • Judges the approximate distance between the vehicle and an obstacle based on the signals from the ultrasonic sensors and sends it to the multi-information display and display and navigation module display*2 or navigation computer sub-assembly*3

    • Sounds the buzzer
    Parking Assist ECU*2, *3 Receives the display signal and sends it to the multi-display*4 through the digital communication cable
    Main Body ECU (Multiplex Network Body ECU) Transmits the destination information to the clearance warning ECU assembly
    Power Management Control ECU Transmits the shift state signal to the clearance warning ECU assembly

    Display and Navigation Module Display*2

    Navigation Computer Sub-assembly*3

    • Receives the ultrasonic sensor information through CAN communication and sends it to the multi-display through the digital communication cable and the multi-media module wire

    • Transmits the customize information on the multi-display to the clearance warning ECU assembly
    Multi-display*4 Receives the display signals from the display and navigation module display*2 or navigation computer sub-assembly*3, and displays them on the display panel.

    • *1: The buzzer does not sound when the power switch is on (IG) while the clearance main switch is on.

    • *2: w/ Navigation System (for DVD)

    • *3: w/ Navigation System (for HDD)

    • *4: w/ Parking Assist Monitor System

    • *5: w/o Parking Assist Monitor System

  3. OPERATION EXPLANATION


    1. The operating conditions of each ultrasonic sensor differ according to the installation position as shown in the table below.

      Installation Position Operating Condition
      Front Corner Sensor

      • Power switch is on (READY).

      • LEXUS parking assist-sensor system is on.

      • A shift state other than park (P) has been selected.

      • Vehicle speed is less than approximately 10 km/h (6.2 mph). The sensors stop operating when the vehicle speed exceeds 15 km/h (9.3 mph), and start operating when the vehicle speed drops below 10 km/h (6.2 mph).
      Rear Corner Sensor

      • Power switch is on (READY).

      • LEXUS parking assist-sensor system is on.

      • Reverse (R) has been selected.
      Rear Center Sensor

      • Power switch is on (READY).

      • LEXUS parking assist-sensor system is on.

      • Reverse (R) has been selected.

      When the system operates, the clearance warning ECU assembly transmits ultrasonic waves from the ultrasonic sensors. If these waves encounter an obstacle within one or more of the sensors ranges, the waves are reflected back to the sensors, which transmit them to the clearance warning ECU assembly.

      Based on this information, the clearance warning ECU assembly sends signals to the indicator and the clearance warning buzzer. The appropriate distance between the vehicle and the obstacle is then indicated, and the buzzer sounds.

      Tech Tips

      Refer to Detection Range Measurement and Display Inspection Click here.

  4. COMMUNICATION SIGNALS OF COMPONENTS

    Tech Tips


    • Allocation refers to the process of the clearance warning ECU assembly setting aside IDs for the sensors.

    • The vehicle has the sensors arranged in 2 groups. There is a front series and a rear series. The sensors are connected in a "daisy chain".


    1. Initialization mode:

      An ID is allocated to each sensor and sensor diagnosis is performed.

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      1. When the initial check is operating (the power switch is on (IG) and the LEXUS parking assist-sensor system is on), the clearance warning ECU assembly provides power to the first sensors in each series (front left sensor and rear right sensor).

        Tech Tips

        Refer to Self-check Function Inspection (Initial Check) Click here.

      2. After the power is supplied, the front left sensor and rear right sensor enter standby mode to receive an ID from the ECU. When a certain amount of time has elapsed, the ECU sends an ID allocation signal to these sensors.

      3. The front left sensor and rear right sensor receive the ID allocation signal from the ECU and perform self-diagnosis. When the sensor self-diagnosis is completed, the ECU sends an ID allocation confirmation signal to these sensors.

      4. After the ID allocation confirmation is performed, the ECU provides power to the second sensors in each series (front right sensor and rear right center sensor) via the first sensors. In the same manner as the first sensors, the second sensors enter standby mode. When a certain amount of time has elapsed, the ECU sends an ID allocation signal to the second sensors.

      5. The above operation will be repeated until an ID is allocated to the last sensor, which is in the rear series (rear left sensor). Initialization ends when ID allocation to all ultrasonic sensors is completed.

    2. Detection mode:

      After initialization mode is completed, the system switches into detection mode. In detection mode, the clearance warning ECU assembly sends information request signals and sensor activation signals to the ultrasonic sensors and receives detection result signals from the sensors.


      1. The ECU regularly sends ID signals, information request signals, and sensor activation signals to each ultrasonic sensor according to the communication schedule.

      2. When a certain amount of time has elapsed (sensor detection operation is completed), the ECU sends an ID signal to the sensor to receive a detection result signal.

      3. The ultrasonic sensor sends a detection result signal or detection information signal to the ECU.

      4. The above operation is performed repeatedly for each ultrasonic sensor.