The Mazda radar cruise control (MRCC) system maintains headway control with a vehicle ahead without the driver having to depress the accelerator or brake pedals so that a constant vehicle speed can be maintained.
When there is no vehicle ahead, the system switches to constant speed driving at the set speed. In addition, if there is a vehicle ahead which is traveling at a speed less than the set speed, the system performs headway control maintaining a constant distance with the vehicle ahead.
WARNING:
Do not rely completely on the MRCC system and always drive carefully.
There are limitations to the distance between the vehicles which can be controlled by the MRCC system, and if the accelerator pedal or brake pedal is mistakenly operated it could result in an accident.
Always verify the safety of the surrounding area and depress the brake pedal while keeping a safe distance from the vehicle ahead.
The MRCC system does not completely stop the vehicle using the automatic braking operation.
Additionally, brake control is performed, however, there are limitations to the deceleration, and the system may be unable to decelerate sufficiently to avoid hitting the vehicle ahead if the vehicle ahead applies the brakes suddenly or another vehicle cuts into the driving lane, which could result in an accident.
Always verify the safety of the surrounding area and depress the brake pedal while keeping a safe distance from the vehicle ahead.
The MRCC system may not operate under the following conditions:
If there is the possibility of hitting only a part of a vehicle or obstruction ahead.
If the vehicle is accelerated rapidly and it comes close to a vehicle ahead.
The DSC HU/CM is malfunctioning.
The vehicle is driven at the same speed as the vehicle ahead.
The accelerator pedal is depressed.
The brake pedal is depressed.
The steering wheel is being operated.
The selector lever is being operated.
The turn signal is being used.
If the radar sensor aiming adjustment for the MRCC system is not completed, a deviation in the radar emission range may occur which could result in an accident. When performing the following servicing, always perform the radar sensor aiming adjustment. Refer to the radar sensor aiming adjustment procedure in the workshop manual.
Vehicle control module (V/C-module) removal/installation, replacement
Radar sensor, radar sensor bracket removal/installation, replacement
Input/output of each signal is performed via CAN.
The CAN utilized between the vehicle control module and the radar sensor is independent of other units.
Block diagram (MRCC/FOW)
MRCC system is equipped with the following indicated modes.
Constant speed mode: Travel at set speed.
Headway control mode: Headway control with vehicle ahead within set vehicle speed
The MRCC operates when all of the following conditions are met.
Selector lever is in D or M position (ATX)
Shift lever in position other than R or N position (MTX)
Vehicle speed within range of approx. 33—144 km/h {21.0—89.4 mph}
MRCC is on
Brake pedal is not depressed
Clutch pedal is not depressed (MTX)
DSC is not operating
TCS is not operating
Smart city brake support (SCBS) is not operating
Parking brake is released
DSC is operating normally (No DTC is stored)
MRCC is operating normally (No DTC is stored)
When the upper or lower part of the switch is pressed while the MRCC system is on and the target vehicle speed is set, the constant speed mode begins operation.
The vehicle control module (V/C-module) indicates the target acceleration rate command value relative to the PCM so that the set vehicle speed can be maintained.
For whatever cause, if the vehicle speed decreases to approx. 25 km/h {16 mph} or lower, the vehicle control module (V/C-module) cancels the MRCC control and transitions it to standby.
If a vehicle ahead is detected by the signal from the radar sensor, the vehicle control module (V/C-module) transitions the system to headway control.
If another vehicle (vehicle ahead) is detected by the signal from the radar sensor while the vehicle is traveling in constant speed control mode, the vehicle control module (V/C-module) transitions the system to headway control mode.
When the system transitions to headway control mode, the vehicle ahead is indicated in the display of the instrument cluster to notify the driver that the system is in headway control mode.
If the vehicle ahead is slower than the set speed of the detecting vehicle, the vehicle control module (V/C-module) sends a brake operation command signal to the DSC HU/CM, the DSC HU/CM operates the brakes, and the vehicle decelerates gradually according to the speed of the vehicle ahead to maintain a certain headway distance.
In the following cases, the system transitions from headway control mode to constant speed mode.
Vehicle ahead accelerates over set vehicle speed of detecting vehicle
Vehicle ahead or detecting vehicle switches driving lanes and vehicle ahead of detecting vehicle no longer exists
Headway control determination
The vehicle control module (V/C-module) receives the yaw rate signal (vehicle cornering speed) and the vehicle speed signal to estimate the travel path of the detecting vehicle.
If the radar sensor detects several vehicles (vehicles ahead) ahead of the detecting vehicle, the system determines headway control for the vehicle which is traveling in the estimated path of travel.
Distance between vehicles table (reference)Distance between vehicle setting
When the DISTANCE switch is pressed, the setting switches in 4 stages: Long, Medium, Short, Extremely short. (Initial setting is "Long".)
| Set distance between vehicles | Detecting vehicle speed |
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| 30 km/h {19 mph} | 40 km/h {25 mph} | 50 km/h {31 mph} | 60 km/h {37 mph} | 70 km/h {43 mph} | 80 km/h {50 mph} | 90 km/h {56 mph} |
|
| Long | 23 m {75 ft} | 29 m {95 ft} | 36 m {118 ft} | 42 m {138 ft} | 48 m {157 ft} | 55 m {180 ft} | 61 m {200 ft} |
| Medium | 19 m {62 ft} | 24 m {79 ft} | 29 m {95 ft} | 34 m {112 ft} | 39 m {128 ft} | 44 m {144 ft} | 49 m {161 ft} |
| Short | 15 m {49 ft} | 18 m {59 ft} | 22 m {72 ft} | 25 m {82 ft} | 29 m {95 ft} | 32 m {105 ft} | 36 m {118 ft} |
| Extremely short | 12 m {39 ft} | 14 m {46 ft} | 17 m {56 ft} | 20 m {66 ft} | 22 m {72 ft} | 25 m {82 ft} | 27 m {89 ft} |
| Set distance between vehicles | Detecting vehicle speed |
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| 100 km/h {62.1 mph} | 110 km/h {68.4 mph} | 120 km/h {74.6 mph} | 130 km/h {80.8 mph} | 140 km/h {87.0 mph} | 150 km/h {93.2 mph} |
||
| Long | 67 m {220 ft} | 74 m {243 ft} | 80 m {262 ft} | 86 m {282 ft} | 93 m {305 ft} | 99 m {325 ft} |
|
| Medium | 53 m {174 ft} | 58 m {190 ft} | 63 m {207 ft} | 68 m {223 ft} | 73 m {240 ft} | 78 m {256 ft} |
|
| Short | 40 m {131 ft} | 43 m {141 ft} | 47 m {154 ft} | 50 m {164 ft} | 54 m {177 ft} | 57 m {187 ft} |
|
| Extremely short | 30 m {98 ft} | 32 m {105 ft} | 35 m {115 ft} | 38 m {125 ft} | 40 m {131 ft} | 43 m {141 ft} |
|
CAUTION:
The distances between vehicles indicated above are average values during fixed travel and differ depending on the driving and road conditions.
Distance between vehicles control
The vehicle control module (V/C-module) calculates the target acceleration rate from the speed of the detecting vehicle, adding the distance between vehicles set by the driver and the distance to the vehicle ahead/relative vehicle speed, and indicates the target acceleration rate command value to the PCM.
If any of the following conditions is met, the warning alarm in the instrument cluster is sounded and the brake warning in the display is indicated to urge the driver to apply the brakes.
Vehicle control module (V/C-module) determines that crash is unavoidable even if automatic braking is performed at possible maximum deceleration rate
Vehicle ahead performs emergency braking
If the transaxle gear position is not appropriate to the vehicle speed while the MRCC system is operating, a shift up/shift down request is displayed in the display of the instrument cluster.
CAUTION:
If the vehicle continues to be driven while not heeding a shift up request, load to the engine will be applied and cause engine damage. Shift the gears up in accordance with the shift up request.
If the vehicle continues to be driven while not heeding a shift down request, the engine will stall. Shift the gears down in accordance with the shift down request.
If the vehicle continues to be driven while not heeding a shift up/down request, load to the engine will be decreased and the vehicle control module will cancel the MRCC automatically.
NOTE:
When driving on a steep downhill, a shift down request may be indicated to decrease the load on the brakes required to maintain a constant vehicle speed.