Mazda X-5. Manual — part 65

DYNAMIC STABILITY CONTROL

04–15–11

04–15

DSC CM PART FUNCTION

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• The DSC CM makes calculations using signals input from each sensor, outputs a brake fluid pressure control

signal to the DSC HU to actuate DSC system functions and outputs an engine output control signal to the PCM.

• The DSC HU/CM controls the following functions:

Function Table

Function name

Contents

ABS control function

• Controls brake fluid pressure when braking to maintain directional

stability, ensure steerability and reduce stopping distance.

EBD (Electronic Brakeforce Distribution) control
function

• Constantly controls proper distribution of brake fluid pressure to the front

and rear wheels according to vehicle load, road surface and vehicle
speed conditions to prevent early lock-up of the rear wheels.

TCS control function

• Controls traction to within the road surface friction limit and according to

road and driving conditions to improve starting and acceleration
performance, and safety.

DSC control function

• Suppresses strong over-steer and under-steer tendencies when turning

by controlling engine output and braking of each wheel to assure driving
safety.

CAN signal function

• Transmits the wheel speed signal to the PCM using CAN

communication.

On-board diagnostic system

• A function that allows important parts of the DSC control system to

perform self-diagnosis. In case a malfunction occurs, the warning lights
illuminate to alert the driver, and at the same time a DTC is stored in the
DSC HU/CM.

• When a malfunction is determined as a result of the on-board diagnosis

test, system control is suspended or limited to prevent any dangerous
situation while driving.

DYNAMIC STABILITY CONTROL

04–15–12

Block Diagram

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ABS CONTROL FUNCTION

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• ABS control is basically the same as that for vehicles with ABS. However, fluid pressure in each wheel is under

independent control in this system.

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EBD CONTROL FUNCTION

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• EBD control has an independent control system for the front and rear wheels, as well as vehicles with ABS,

which constantly and properly distributes brake fluid regardless of vehicle weight (number of passengers).

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INPUT

ABS WHEEL-
SPEED SENSOR

BRAKE SWITCH

PCM

ENGINE SPEED

THROTTLE
OPENING ANGLE

OUTPUT TORQUE/
TORQUE REDUCTION
INHIBITED

DSC OFF SWITCH

STEERING
ANGLE SENSOR

COMBINED SENSOR

YAW RATE
SENSOR

LATERAL-G
SENSOR

BRAKE FLUID
PRESSURE SENSOR

CM INTERNAL CALCULATION

WHEEL-SPEED
CALCULATION

ESTIMATED VEHICLE
SPEED CALCULATION

BRAKE OPERATING
CONDITION DETERMINATION

ENGINE SPEED
CALCULATION

THROTTLE OPENING
ANGLE DATA ASSIMILATED

OUTPUT TORQUE/
TORQUE RESUCTION
INHIBITED DATA ASSIMILATED

DSC OFF REQUIREMENT
DETERMINED

YAW RATE
CALCULATION

LATERAL-G
CALCULATION

MASTER CYLINDER FLUID
PRESSURE CALCULATION

DSC
CONTROL
AMOUNT

TCS
CONTROL
AMOUNT

EBD
CONTROL
AMOUNT

ABS
CONTROL
AMOUNT

OUTPUT

PUMP
MOTOR

FRONT
SOLENOID
VALVE

REAR
SOLENOID
VALVE

PCM

TRACTION
CONTROL
SOLENOID
VALVE

STABILITY
CONTROL
SOLENOID
VALVE

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DYNAMIC STABILITY CONTROL

04–15–13

04–15

TCS CONTROL OUTLINE

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• TCS control actuates torque reduction through throttle, fuel cut and ignition timing control, as well as using

brake control to control traction.

Note

• Brake control: Brake fluid pressure from the hydraulic unit to the slipping driving wheel is increased,

operating the brake and preventing drive wheel slip.

Features

• The left and right wheels are controlled at the same time by throttle, fuel cut and ignition timing control.

Therefore, when the road surface friction coefficients differ between the left and right wheels, proper torque
reduction cannot be performed separately for each wheel. When this occurs, torque reduction is performed by
independent left and right wheel brake control, providing much stable vehicle control.

Block Diagram

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TCS CONTROL OPERATION

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• TCS control detects a slipping drive wheel using the following signals, sends a torque reduction request signal

to the PCM and, at the same time, controls the solenoid valves and pump motor in the DSC HU/CM.

— Vehicle wheel speed signals from the front and rear ABS wheel-speed sensors

— Engine torque signal from the PCM

— Steering angle signal from the steering angle sensor

— Yaw rate and lateral-G signals from the combined sensor

— Fluid pressure signals from the brake fluid pressure sensors

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BRAKE FLUID
PRESSURE
SENSOR

DSC HU/CM

ABS WHEEL-SPEED
SENSOR (LF)

ABS WHEEL-SPEED
SENSOR (RF)

ABS WHEEL-SPEED
SENSOR (LR)

ABS WHEEL-SPEED
SENSOR (RR)

STEERING ANGLE
SENSOR

COMBINED
SENSOR

CPU

CM

HU

SOLENOID
VALVE

PUMP
MOTOR

PCM

CALIPER PISTON
(RR)

CALIPER PISTON
(LR)

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DYNAMIC STABILITY CONTROL

04–15–14

DSC CONTROL OUTLINE

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• While a vehicle normally turns safely in response to steering operation, there are instances when the limits of

tire lateral grip is surpassed due to road surface conditions or vehicle speed, and the influence of evasive
steering to avoid an accident or similar situations.

• Tires surpassing lateral grip exhibit one of the following conditions:

— Strong oversteer tendency: The rear wheels are relatively losing their grip as compared to the front wheels

— Strong understeer tendency: The front wheels are relatively losing their grip as compared to the rear

wheels

• DSC operates at vehicle speeds of 10 km/h {6.2 mph} or more in the conditions described above, controlling

engine output and wheel braking to suppress oversteer and understeer tendencies.

Vehicle Condition Determination

• The vehicle speed, steering angle, lateral-G and yaw rate are detected by the sensors and used in calculations

by the DSC HU/CM to determine the vehicle condition. Then, depending on the difference between the target
yaw rate, calculated with the values input from each sensor, and the value detected by the yaw rate sensor, an
oversteer or understeer tendency can be determined.

Oversteer Tendency Determination

• When turning, if the actual vehicle yaw rate is larger than the target yaw rate (the yaw rate that should normally

be formed as determined by the steering angle and vehicle speed), it means that the vehicle is in or about to be
in a spin. Therefore the vehicle is determined to have an oversteer tendency.

Understeer Tendency Determination

• When turning, if the actual vehicle yaw rate is less than the target yaw rate (the yaw rate that should normally

be formed as determined by the steering angle and vehicle speed), it means that the vehicle is not properly
turning. Therefore the vehicle is determined to have an understeer tendency.

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YAW MOMENTUM

UNDERSTEER CONDITION
LINE OF TRAVEL

TARGET YAW RATE
LINE OF TRAVEL

OVERSTEER CONDITION
LINE OF TRAVEL

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