FUNCTION OF MAIN COMPONENTS
The main components in the dynamic radar cruise control system have the following functions:
| Component | Function | ||
|---|---|---|---|
| Cruise Control Switch | ON-OFF/ Mode Button |
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| 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 | Vehicle-to-vehicle Distance Control Switch | While the system is in vehicle-to-vehicle distance control mode, the driver can operate the vehicle-to-vehicle 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. | ||
| Forward Recognition Camera | Detects lane markers and objects on the road ahead using the image captured by the monocular camera and sends the 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 assembly and forward recognition camera. 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. | ||
| Combination Meter Assembly | Multi-information Display | Cruise Control Indicator (Constant Speed Control Mode) | Illuminates when constant speed control mode is entered. |
| Cruise Control Indicator (Vehicle-to-vehicle Distance Control Mode) | Illuminates when the cruise control switch ON-OFF button is pressed to start the cruise control system. | ||
| Cruise Control SET Indicator | Illuminates when the vehicle speed is set. | ||
| Multi-information Display | During dynamic radar cruise control operation, the multi-information display receives signals from the ECM in order to display the system conditions. | ||
| Buzzer | If the ECM detects automatic cancel or warning signals while the vehicle is operating under cruise control, this buzzer sounds to inform the driver. | ||
| Master Warning Light | Comes on when there is a malfunction in the system. | ||
| 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 |
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| ECM |
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| 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 |
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| Accelerator Pedal Sensor Assembly | Detects the accelerator pedal depression degree and outputs it to the ECM. | ||
Tech Tips
*: Models with 2GR-EF Engine
SYSTEM CONTROL
The driving support ECU assembly, millimeter wave radar sensor assembly, forward recognition camera and ECM control this system.
The combination meter assembly informs the driver of the control conditions.
Constant speed control mode is controlled by the ECM, which outputs signals to the throttle control motor and the TCM.
Vehicle-to-vehicle distance control mode is controlled by the millimeter wave radar sensor assembly, forward recognition camera and driving support ECU assembly. Thus, the signals are output to the actuators and the ECU while exchanging data as indicated below.
| *1 | Driving Support ECU Assembly |
| *2 | Forward Recognition Camera |
| *3 | Millimeter Wave Radar Sensor Assembly |
| *4 | CAN Communication Line |
FUNCTION
Function List
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 assembly, forward recognition camera 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 vehicle is traveling at a speed within the range of approximately 50 km/h to 200km/h (30 mph to 125 mph). | ○ | - | |
| The vehicle is traveling at a speed within the range of approximately 50 km/h to 180 km/h (30 mph to 110 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: | ○ | ○ |
|
○ | - | |
|
- | ○ | |
| 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 km/h or 1 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: | ○ | ○ |
|
○ | - | |
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- | ○ | |
| RES Switch Control | When the vehicle speed is above the low speed limit, the cruise control system resumes operation (when the cruise control switch is subsequently moved 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. Also, If the vehicle speed memory is deleted, the return control cannot be performed. | ○ | ○ |
| When the vehicle ahead changes driving lanes during follow-up control, the vehicle speed is gradually increased to the set speed. At this time, the vehicle speed can be increased promptly by pushing the cruise control switch to the +RES direction. | - | ○ | |
| 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 km/h or 1 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.
|
○ | ○ |
| 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. | ○ | ○ |
| Other Cancel Conditions |
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○ | ○ |
| Mode Switching Control | The following operations switch modes:
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○ | ○ |
| 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
Constant Speed Control in Vehicle-to-vehicle Distance Control
The millimeter wave radar sensor assembly and forward recognition camera transmits the information about the vehicle ahead to the driving support ECU assembly and also transmits a millimeter wave radar sensor assembly 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.
Deceleration Control
The driving support ECU assembly calculates the target deceleration rate in accordance with signals from the millimeter wave radar sensor assembly, forward recognition camera 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.
This control is not performed in the presence of a parked vehicle or object, or below the settable vehicle speed range.
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.
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.
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.
Follow-up Control
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.
3 stages (long, middle, and short) of vehicle-to-vehicle distance can be selected by operating the distance control switch.
Acceleration Control
If the driving support ECU assembly detects (based on the millimeter wave radar sensor assembly and forward recognition camera ) that either the vehicle ahead or the driver 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.
Automatic Cancel Control
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.
| Situation | Warning | ||
|---|---|---|---|
| Multi-information Display | |
Buzzer in the combination meter assembly | |
|
Cruise Control Malfunction Visit Your Dealer | Illuminates | Sounds once |
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Cruise Control Malfunction Visit Your Dealer | Illuminates | Sounds once |
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- | - | - |
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- | - | - |
|
- | - | - |
| Situation | Warning | ||
|---|---|---|---|
| Multi-information Display | |
Buzzer in the combination meter assembly | |
|
Cruise Control Malfunction Visit Your Dealer | Illuminates | Sounds once |
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Cruise Control Malfunction Visit Your Dealer | Illuminates | Sounds once |
|
- | - | - |
|
Radar Cruise Control Unavailable Clean Radar Sensor | Illuminates | Sounds once |
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Radar Cruise Control Unavailable | Illuminates | Sounds once |
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- | - | Sounds twice |
CONSTRUCTION
Cruise Control Switch
The cruise control switch consists of the ON-OFF/ Mode button and the +RES, -SET and CANCEL switches. The ON-OFF/ Mode button, +RES, -SET and CANCEL switches are operated by moving the lever in the 4 directions indicated.
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.
| *1 | Vehicle-to-vehicle Distance Control Switch | *2 | Cruise Control Switch |
| *a | ON-OFF/ Mode Button | *b | +RES Switch |
| *c | -SET Switch | *d | CANCEL Switch |
Main switch (ON-OFF)/ Mode Button
When the cruise control system is turned on using the main switch (ON-OFF button), the system starts in vehicle-to-vehicle distance control mode. When the main switch (ON-OFF button) is pressed and held for 1.5 seconds or more, the system changes to constant control mode.
Vehicle-to-vehicle Distance Control Switch
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 → long.
If the engine switch is turned off and back on (IG), the system will default to "long".
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).
Millimeter Wave Radar Sensor Assembly
The millimeter wave radar sensor assembly consists of a millimeter wave radar circuit, signal processing circuit, and CPU.
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.*
Tech Tips
*: The millimeter wave radar sensor assembly outputs varies by destination.
The antennas receive the reflected millimeter waves.
The signal processing circuit detects the distance, relative speed, and the direction of the object by generating millimeter waves and calculating the signals received by the antennas.
| *1 | Millimeter Wave Radar Sensor Assembly | - | - |
| *a | Detection Distance: Approximately 150 m (490 ft.) | *b | Horizontal Angle: Approximately 20° |
| *c | Vertical Angle: Approximately 4° | *d | Signal Processing Circuit |
| *e | Millimeter Wave Radar Circuit | - | - |
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 4°. |
| 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.
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-collision system uses frequencies in the 76 GHz band.
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-collision 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.
Forward Recognition Camera
Forward recognition camera is mounted in the upper center of the windshield glass. The sensor detects vehicles and other objects on the road ahead using the image captured by the built-in monocular camera and determines their distance. With this, the recognition performance and reliability of the dynamic radar cruise control system has been enhanced.
| *1 | Forward Recognition Camera | - | - |
| *a | Monocular Camera | *b | Approximately 50 m (164 ft.) |
OPERATION
Combination Meter Assembly
The combination meter assembly has a master warning light, cruise control indicator (constant speed control mode), cruise control indicator (vehicle-to-vehicle distance control mode), cruise control SET indicator, buzzer, and multi-information display to provide warnings and messages regarding the dynamic radar cruise control system.
The multi-information display displays the set vehicle speed, vehicle ahead mark, and warning message.
Examples are shown below for the illumination or display of each indicator light, warning light or multi-information display.
| Condition | Multi-information Display | |
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Buzzer |
|---|---|---|---|---|---|---|
| Being Controlled* | |
Does not illuminate | Illuminates | Does not illuminate | Illuminates | - |
| System Check | Cruise Control Malfunction Visit Your Dealer | 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 90 km/h (56 mph).
| Condition | Multi-information Display | |
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Buzzer |
|---|---|---|---|---|---|---|
| Set Standby | |
Does not illuminate | Does not illuminate | Illuminates | Does not illuminate | - |
| Under Constant Speed Control (No Vehicle Ahead, Short)* | |
Does not illuminate | Does not illuminate | Illuminates | Illuminates | - |
| Under Follow-up Control (Vehicle Ahead, Long)* | |
Does not illuminate | Does not illuminate | Illuminates | Illuminates | - |
| Deceleration Control/Vehicle Approach Warning (Vehicle Ahead, Middle)* | |
Does not illuminate | Does not illuminate | Illuminates | Illuminates | Skid control buzzer sounds continuously |
| Blinks | ||||||
| Millimeter Wave Radar Sensor Assembly is Dirty. | Radar Cruise Control Unavailable Clean Sensor | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
| Poor Weather Conditions A Malfunction in the forward recognition camera Misalignment of the axis of the millimeter wave radar sensor assembly. |
Radar Cruise Control Unavailable | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
| System Check | Cruise Control Malfunction Visit Your Dealer | Illuminates | Does not illuminate | Does not illuminate | Does not illuminate | Buzzer in the combination meter assembly sounds once |
| Beam Axis Adjustment | Adjusting Front Radar Beam | Does not illuminate | Does not illuminate | Does not illuminate | Does not illuminate | - |
Tech Tips
*: While driving at a set speed of 90 km/h (56 mph).
DIAGNOSIS
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 "Cruise Control Malfunction Visit Your Dealer" 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).
The 5-digit DTC can be read by connecting the Global TechStream (GTS) to the DLC3. For details, refer to the Repair Manual.