DYNAMIC RADAR CRUISE CONTROL SYSTEM DETAILS


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components in the dynamic radar cruise control system have the following functions:

      Component Function
      Cruise Control Switch ON-OFF Button Turns the cruise control system on and off.
      MODE Switch Switches the control mode between constant speed control mode and vehicle-to-vehicle distance mode.
      CANCEL Switch A cancel signal is output to the ECM when this switch is operated.
      RES/+ Switch The acceleration function and resuming of a preset speed can be performed by operating this switch. A signal is output to the ECM when this switch is operated.
      SET/- Switch The deceleration function and vehicle speed setting resume signals are output to the ECM when this switch is operated.
      Steering Pad Switch Assembly Distance Control Switch While the system is in vehicle-to-vehicle distance control mode, the driver can operate the distance control switch to select the vehicle-to-vehicle distance in three levels: long, middle and short.
      Stop Light Switch Assembly Detects brake pedal depression and transmits its signal to the ECM.
      Windshield Wiper Motor Assembly Transmits the windshield wiper motor assembly information to the driving support ECU assembly.
      Millimeter Wave Radar Sensor Assembly Radiates millimeter radar waves forward, uses the reflected waves to detect 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.
      Driving Support ECU Assembly While the system is in vehicle-to-vehicle distance control mode, the driving support ECU assembly detects the vehicle ahead based on signals from the millimeter wave radar sensor. Then, the driving support ECU assembly calculates the acceleration or deceleration rate required in order to attain the target vehicle-to-vehicle distance, and outputs a request signal to the ECM and/or skid control ECU (brake actuator assembly).
      Combination Meter Assembly Cruise Control Indicator Light (Constant Speed Control Mode) Comes on when constant speed control mode is entered.
      Cruise Control Indicator Light (Vehicle-to-vehicle Distance Control Mode) Comes on when the cruise control switch ON-OFF button is pressed to start the cruise control system.
      Master Warning Light Comes on when there is a malfunction in the system.
      Buzzer If the ECM or driving support ECU assembly detects automatic cancel or warning signals while the vehicle is operating under cruise control, this buzzer sounds to inform the driver.
      Multi-information Display During dynamic radar cruise control operation, the multi-information display receives signals from the driving support ECU assembly in order to display the system conditions.
      Steering Sensor Detects the angle and direction of steering and transmits signals to the skid control ECU assembly and driving support ECU assembly.
      Airbag Sensor Assembly Yawrate Sensor Detects the yaw rate of the vehicle and transmits signals to the skid control ECU assembly and driving support ECU assembly.
      Brake Actuator Assembly Skid Control ECU

      • While the system is operating in vehicle-to-vehicle distance control mode, the skid control ECU assembly operates the brake actuator in accordance with the brake request signal received from the ECM.

      • Applies the brakes in accordance with signals from the skid control ECU.
      ECM

      • Controls the dynamic radar cruise control system in accordance with signals from the switches, sensors, skid control ECU assembly and driving support ECU assembly.

      • If the ECM detects a malfunction in the cruise control system, it will store Diagnostic Trouble Codes (DTCs).
      TCM* Performs downshifts and upshifts according to signals from the ECM.
      Park/Neutral Position Switch Assembly Detects the shift lever position and transmits signals to the ECM.
      Lower Shift Lever Assembly Transmission Control Switch

      • Detects the shift lever position and transmits signals to the ECM.

      • Informs the ECM of driver upshift or downshift operations while the shift lever is in S.
      Accelerator Pedal Sensor Assembly Detects the accelerator pedal depression degree and outputs it to the ECM.

      *: Models with 2GR-FE engine

  2. SYSTEM CONTROL


    1. The driving support ECU assembly, millimeter wave radar sensor and ECM control this system.

    2. The combination meter assembly informs the driver of the control conditions.

    3. Constant speed control mode is controlled by the ECM, which outputs signals to the throttle control motor and the TCM*.

      *: Models with 2GR-FE engine

      A01GVU1E02

    4. Vehicle-to-vehicle distance control mode is controlled by the millimeter wave radar sensor and driving support ECU assembly. Thus, the signals are output to the actuators and the ECU while exchanging data as indicated below.

      A01GVHIE01

  3. FUNCTION


    1. Function List


      1. The control of the dynamic radar cruise control system varies depending on the mode:

        A: Constant Speed Control Mode

        B: Vehicle-to-vehicle Distance Control Mode

        Function Outline Mode
        A B
        Constant Speed Control The ECM compares the actual vehicle speed and the set speed and if the vehicle speed is lower than the set speed, it uses the throttle motor to increase the throttle opening. ○ ○
        In constant speed control mode, constant speed control is performed by the ECM in the same way as conventional cruise control. ○ -
        In vehicle-to-vehicle distance control mode, constant speed control is performed by the millimeter wave radar sensor and driving support ECU assembly. - ○
        Deceleration Control Performs throttle control and brake control in order to decelerate the vehicle so that the vehicle-to-vehicle distance between the driver's own vehicle and the vehicle ahead equals the set distance. - ○
        Follow-up Control After performing deceleration control, the driver's own vehicle follows the vehicle ahead in order to maintain the proper vehicle-to-vehicle distance in accordance with the vehicle speed. - ○
        Acceleration Control Accelerates the vehicle in order to attain the set vehicle speed if the vehicle ahead or the driver's own vehicle has changed lanes. - ○
        Set Control

        When the following conditions are met, and the cruise control switch is pressed to the -/SET side and released, the ECM stores the vehicle speed and maintains the vehicle constantly at the current speed.


        • The cruise control system is on.

        • The shift lever is in D or the shift lever is in S with 4th, 5th, or 6th shift range selected.

        		 ○ ○
        The vehicle is traveling at a speed within the range of approximately 50 to 200 km/h (30 to 124 mph). ○ -
        The vehicle is traveling at a speed within the range of approximately 50 to 170 km/h (30 to 105 mph). - ○
        Low Speed Limit Control The low speed limit is the lowest speed that cruise control can be set at and it is designed to be approximately 40 km/h (25 mph). The cruise control cannot be set below that speed. If the vehicle speed drops below that speed while driving using cruise control, the cruise control will be canceled automatically. The set vehicle speed is kept in memory. ○ ○
        COAST Switch Control While the cruise control switch is held to the SET/- side, the vehicle speed and the set vehicle speed change as follows, according to the mode: ○ ○

        • The vehicle decelerates constantly.

        • The set vehicle speed changes to the speed at which the switch is released.

        		 ○ -

        • The set vehicle speed decreases in increments of 5 km/h or 5 mph. [Example: 82 →80 →75 km/h (mph)]

        • The vehicle decelerates rapidly due to ETCS-i. The vehicle will remain at the speed that the vehicle is traveling at when the COAST switch is released.

        		 - ○
        Tap Down Control When the cruise control switch is moved momentarily (approximately 0.6 seconds or less) to the -SET side, the vehicle speed and the set vehicle speed change as follows, according to the mode: ○ ○

        • The vehicle will decelerate in increments of approximately 1.6 km/h (1 mph) each time the switch is moved.

        • However, if the difference between the actual vehicle speed and the set vehicle speed is greater than 5 km/h or 5 mph, the set vehicle speed will change to the speed at which the vehicle was being driven at the time the switch was operated.

        		 ○ -
        The vehicle will decelerate in increments of approximately 5 km/h or 5 mph each time the switch is moved. - ○
        ACC Switch Control When the cruise control switch is held to the RES/+ side, the vehicle speed and the set vehicle speed change as follows, according to the mode: ○ ○

        • The vehicle will accelerate constantly.

        • The set vehicle speed changes to the speed at which the switch is released.

        		 ○ -

        • The set vehicle speed increases in increments of 5 km/h or 5 mph. [Example: 62 →65 →70 km/h (mph)]

        • The vehicle will accelerate to the speed that is set at the time the switch is released. However, only the set vehicle speed will change during follow-up control.

        		 - ○
        RES Switch Control

        If the vehicle speed is above the low speed limit, the cruise control resumes operation (when the cruise control switch is subsequently pushed to the RES/+ side) to reach the vehicle speed that was set at the time the driver canceled cruise control.

        Even if the vehicle speed dropped below the low speed limit, the set speed can be resumed after the vehicle speed increases above the low speed limit.

        		 ○ ○
        Tap Up Control When the cruise control switch is moved momentarily (approximately 0.6 seconds or less) to the +RES side, the vehicle speed and the set vehicle speed change as follows: ○ ○

        • The vehicle will accelerate in increments of approximately 1.6 km/h (1 mph) for each time the switch was moved.

        • However, if the difference between the actual vehicle speed and the set vehicle speed is greater than 5 km/h (3 mph), the set vehicle speed will not change.

        		 ○ -
        The vehicle will accelerate in increments of approximately 5 km/h or 5 mph for each time the switch is moved. - ○
        Shift-down Control When the vehicle is traveling uphill using cruise control, automatic transmission control may cause the transmission to shift down. During shift-down control, when the end of uphill travel is determined based on the throttle valve angle, the transmission will shift up after a certain period of time. When the transmission shifts down during ACC switch control or RES switch control, the transmission will shift up after ACC switch control or RES switch control ends. ○ ○
        Manual Cancel Control

        If one of the following conditions are met, the cruise control is canceled accordingly.


        • Shift lever is moved from D to N.

        • When 1st, 2nd or 3rd shift range is selected manually while in S.

        • Stop light switch on signal (brake pedal is depressed).

        • CANCEL switch on signal sent to the ECM (cruise control switch is moved to CANCEL side).

        • Cruise control switch (ON-OFF button) off signal sent to the ECM.

        • VSC operation signal sent to the ECM.

        		 ○ ○
        Automatic Cancel Control When an automatic cancel signal is sent to the ECM, cruise control operation is canceled. At this time, the type of warning sent to the driver and the control resumption condition varies according to the cancel signal. ○ ○
        Mode Switching Control

        The following operations switch modes:


        • The ON-OFF button on the cruise control switch is turned on. (Starts in vehicle-to-vehicle distance control mode.)

        • The cruise control switch is held to the MODE side. (for approximately 1 second or more). If the switch is pushed to any other side before switching modes, turn the cruise control system off, then, perform the steps above again.

        		 ○ ○
        Diagnosis If a malfunction occurs in the dynamic radar cruise control system during cruise control operation, the ECM cancels cruise control and memorizes information related to the malfunction. ○ ○

        Tech Tips


        • ○: Available

        • -: Not Available

    2. Constant Speed Control in Vehicle-to-vehicle Distance Control

      The millimeter wave radar sensor transmits the information about the vehicle ahead to the driving support ECU assembly and also transmits a millimeter wave radar sensor operation signal to the ECM via the driving support ECU assembly. The ECM compares the set vehicle speed and the actual vehicle speed, and performs constant speed control by regulating the throttle in order to attain the set vehicle speed.

      A01GVHOE01

    3. Deceleration Control


      1. The driving support ECU assembly calculates the target deceleration rate in accordance with signals from the millimeter wave radar sensor, and transmits a deceleration request signal to the ECM. Upon receiving this signal, the ECM closes the throttle valve in order to cause the vehicle to decelerate.

      2. This control is not performed in the presence of a parked vehicle or object, or below the settable vehicle speed range.

        A01GVTTE01

      3. If the driving support ECU assembly determines that further deceleration is necessary, it transmits a brake request signal to the ECM. Upon receiving this signal, the ECM transmits a brake request signal to the skid control ECU. The skid control ECU then controls the brake actuator to apply the brakes.

      4. At this time, if the deceleration rate is higher than a predetermined value, the skid control ECU outputs a stop light illumination request signal to the stop light, order to warn any vehicles behind.

        A01GVQKE01

      5. If the vehicle is not decelerating adequately, the driving support ECU assembly sounds a skid control buzzer assembly to prompt the driver to apply the brakes.

        A01GVTLE01

    4. Follow-up Control


      1. After performing deceleration control, the driving support ECU assembly transmits a request signal to the ECM so that the vehicle can follow the vehicle ahead while maintaining the proper vehicle-to-vehicle distance according to the vehicle speed. Upon receiving this signal, the ECM regulates the throttle in order to perform follow-up control.

      2. 3 stages (long, middle, and short) of vehicle-to-vehicle distance can be selected by operating the distance control switch.

        A01GVMTE01

    5. Acceleration Control


      1. If the driving support ECU assembly detects (based on the millimeter wave radar sensor) that either the vehicle ahead or own vehicle has changed lanes, an acceleration request signal is transmitted to the ECM in order to attain the set vehicle speed. Upon receiving this signal, the ECM regulates the throttle in order to perform acceleration control.

        A01GVUHE01

    6. Automatic Cancel Control


      1. If one of the conditions listed below occurs while the vehicle is being driven using cruise control, the cruise control will be canceled. Then, the following warning items will appear for the driver.

        Constant Speed Control Mode:
        Situation Warning
        Multi-information Display A01GVAY A01GW05 A01GV9H A01GVQY Buzzer in the combination meter assembly

        • If either of the conditions listed below occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • A malfunction of the vehicle speed signal (SPD)

          • An open or short circuit in the stop light switch


        • Cruise control is prohibited until the normal operating condition is met or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control switch.

        		 A01GVGJ Illuminates Does not illuminate Does not illuminate Does not illuminate Sounds once

        • If either of the conditions listed below occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • Stop light switch assembly input signal is abnormal.

          • Cancel circuit malfunction


        • The cruise control is disabled until the engine switch is turned on (IG) again.

        		 A01GVGJ Illuminates Does not illuminate Does not illuminate Does not illuminate Sounds once

        • If the following condition occurs, the ECM cancels the cruise control while retaining the set vehicle speed in its memory.


          • The vehicle speed drops below the low speed limit [approx. 40 km/h (25 mph)].

        		 - Does not illuminate Does not illuminate Does not illuminate Does not illuminate -

        • If the following condition occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • The vehicle speed drops more than 16 km/h (10 mph) below the set vehicle speed.

        		 - Does not illuminate Does not illuminate Does not illuminate Does not illuminate -

        • If the following condition occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • A malfunction in the ETCS-i.


        • Cruise control is prohibited until the normal operating conditions are met or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control switch.

        		 - Does not illuminate Does not illuminate Does not illuminate Does not illuminate -
        Vehicle-to-vehicle Distance Control Mode:
        Situation Warning
        Multi-information Display A01GVAY A01GW05 A01GV9H A01GVQY Buzzer in the combination meter assembly

        • If either of the conditions listed below occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • A malfunction of the vehicle speed signal (SPD).

          • An open or short circuit in the stop light switch


        • Cruise control is prohibited until the normal operating conditions are met or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control switch.

        		 A01GVGJ Illuminates Does not illuminate Does not illuminate Does not illuminate Sounds once

        • If one of the conditions listed below occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • Stop light switch assembly input signal is abnormal.

          • Cancel circuit malfunction

          • Malfunction of the millimeter wave radar sensor assembly

          • Misalignment of the axis of the millimeter wave radar sensor assembly

          • Malfunction in the dynamic radar cruise control system other than those given above


        • The cruise control is disabled until the engine switch is turned on (IG) again.

        		 A01GVGJ Illuminates Does not illuminate Does not illuminate Does not illuminate Sounds once

        • If the following condition occurs, the ECM clears the set vehicle speed and cancels the cruise control.


          • A malfunction in the ETCS-i


        • The cruise control is disabled until the condition is corrected or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control switch.

        		 - Does not illuminate Does not illuminate Does not illuminate Does not illuminate -

        • If the following condition occurs, the ECM cancels the cruise control while retaining the set vehicle speed in its memory.


          • The millimeter wave radar sensor assembly is dirty.


        • Cruise control is prohibited until the normal operating conditions are met or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control switch.

        		 A01GW1S Illuminates Does not illuminate Does not illuminate Does not illuminate Sounds once

        • If either of the following conditions occurs, the ECM cancels the cruise control while retaining the set vehicle speed in its memory.


          • The wipers operate at HI speed.

          • The measurement becomes extremely unstable due to poor weather conditions.


        • Cruise control is prohibited until the normal operating conditions are met or the cruise control system is turned off and back on again using the ON-OFF button on the cruise control switch.

        		 A01GVPD Illuminates Does not illuminate Does not illuminate Does not illuminate Sounds once

        • If the following condition occurs, the ECM cancels the cruise control while retaining the setting vehicle speed in its memory.


          • The vehicle speed drops below the low speed limit [approx. 40 km/h (25 mph)].

        		 - Does not illuminate Does not illuminate Does not illuminate Does not illuminate Sounds twice

  4. CONSTRUCTION


    1. Cruise Control Switch


      1. The cruise control switch consists of the ON-OFF button and the +RES, MODE, -SET and CANCEL switches. The +RES, MODE, -SET and CANCEL switches are operated by moving the lever in the 4 directions indicated.

      2. The cruise control switch is an automatic reset (normally open) type that turns on only when the switch is being operated and turns off as soon as the driver releases the switch. Furthermore, the functions of the control switch are active only when the cruise control system has been turned on using the ON-OFF button on the cruise control switch.

        A01GVUNE01
        Text in Illustration
        *1 Distance Control Switch *2 Cruise Control Switch
        *a ON-OFF Button *b +RES Switch
        *c MODE Switch *d -SET Switch
        *e CANCEL Switch - -

    2. Distance Control Switch


      1. While the vehicle is being driven in vehicle-to-vehicle distance control mode, the vehicle-to-vehicle distance setting can be changed as follows each time the distance control switch is pressed; long → middle → short.

      2. If the engine switch is turned off and back on (IG), the system will default to "long".

      3. The vehicle-to-vehicle distance is as follows:

        Mode Vehicle-to-vehicle Distance*
        Long Approximately 50 m (160 ft.)
        Middle Approximately 40 m (130 ft.)
        Short Approximately 30 m (100 ft.)

        Tech Tips

        *: While driving at a speed of 80 km/h (50 mph).

    3. 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 0 km/h (0 mph), and it does 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.

        A01GVD4E01
        Text in Illustration
        *1 Millimeter Wave Radar Sensor Assembly - -
        *a Detection Distance: Approximately 150 m (490 ft.) *b Horizontal Angle: Approximately 20°
        *c Vertical Angle: Approximately 8° *d Signal Processing Circuit
        *e Millimeter Wave Radar Circuit - -

      5. The distance to the object, azimuth, and relative speed are calculated from the information that is provided by the reflected millimeter wave radar waves 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 reflected waves are received by the millimeter wave radar circuit. The detection distance is approximately 150 m (490 ft.).
        Azimuth Calculated from the reception angle of the reflected millimeter wave radar waves. The detection angle has a horizontal range of approximately 20° and a vertical range of approximately 8°.
        Relative Speed Calculated by utilizing the change (Doppler effect*) that occurs in the frequency 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.

        A01GVZWE07

        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 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.

        A01GVD5E01

  5. OPERATION


    1. Combination Meter Assembly


      1. The combination meter assembly has a master warning light, cruise control indicator light (constant speed control mode), cruise control indicator light (vehicle-to-vehicle distance control mode), cruise control SET indicator light, buzzer, and multi-information display to provide warnings and messages regarding the dynamic radar cruise control system.

      2. The multi-information display displays the set vehicle speed, vehicle ahead mark, and warning message.

      3. Examples are shown below for the illumination or display of each indicator light, warning light or multi-information display.

        Constant Speed Control Mode:
        Condition Multi-information Display A01GVAY A01GW05 A01GV9H A01GVQY Buzzer
        Being Controlled* A01GVET Does not illuminate Illuminates Does not illuminate Illuminates -
        System Check A01GVGJ Illuminates Does not illuminate Does not illuminate Does not illuminate Buzzer in the combination meter assembly sounds once

        Tech Tips

        *: While driving at a set speed of 100 km/h (62 mph).

        Vehicle-to-vehicle Distance Control Mode:
        Condition Multi-information Display A01GVAY A01GW05 A01GV9H A01GVQY Buzzer
        Set Standby A01GVCO Does not illuminate Does not illuminate Illuminates Does not illuminate -
        Under Constant Speed Control (No Vehicle Ahead, Short)* A01GVE1 Does not illuminate Does not illuminate Illuminates Illuminates -
        Under Follow-up Control (Vehicle Ahead, Middle)* A01GVUC Does not illuminate Does not illuminate Illuminates Illuminates -
        Deceleration Control/Vehicle Approach Warning (Vehicle Ahead, Long)* A01GVWX Does not illuminate Does not illuminate Illuminates Illuminates Skid control buzzer sounds continuously
        Blinks
        Millimeter Wave Radar Sensor Assembly is Dirty. A01GW1S Illuminates Does not illuminate Does not illuminate Does not illuminate Buzzer in the combination meter assembly sounds once
        Poor Weather Conditions A01GVPD Illuminates Does not illuminate Does not illuminate Does not illuminate Buzzer in the combination meter assembly sounds once
        System Check A01GVGJ Illuminates Does not illuminate Does not illuminate Does not illuminate Buzzer in the combination meter assembly sounds once
        Beam Axis Adjustment A01GVCJ Does not illuminate Does not illuminate Does not illuminate Does not illuminate -

        Tech Tips

        *: While driving at a set speed of 100 km/h (62 mph).

  6. DIAGNOSIS


    1. If a malfunction occurs in the dynamic radar cruise control system during cruise control operation, the ECM automatically cancels the cruise control, illuminates the master warning light, sounds a buzzer and displays "Check Cruise Control System" on the multi-information display to inform the driver of the malfunction. At this time, the ECM memorizes the malfunction in the form of 5-digit Diagnostic Trouble Codes (DTCs).

    2. DTCs can be read when a Global TechStream (GTS) is connected to the DLC3.

    3. The Global TechStream (GTS) can be used to read the 5-digit codes. For details, refer to the Repair Manual.