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09-28
Front Brake AssemblyFront Wheel Speed Sensor (4WD)
HECU
2. SYSTEM LAYOUT
Master Cylinder and Booster
Brake Pedal
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09-32
4. HYDRAULIC CIRCUIT
Brake booster
Brake fluid reservoir and master cylinder
Front disc brake and caliper 1.
2.
3.HECU (Hydraulic & Electric Control Unit)
Rear disc brake and caliper 4.
5.
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10-34892-01
1. SPECIFICATION
Unit DescriptionSpecification
Remark
ABS ESP
HECU Clock frequency 32MHz 50MHz
Memory 128KB 256KB
S-sensor Operating voltage 4.75~5.25V
None (functions in
sensor cluster)Installed in IP
panel behind
audio (only for
4WD) Operating temperature-30 ~ 85℃
Operating range -1.5 ~ 1.5g
Output voltage 0.5 ~ 4.5V
Wheel speed
sensorSupplying voltage 4.5 ~ 16V←
Output current (approx. 2.7
km/h of vehicle speed)7mA(Lo) ~ 14mA
+20%←
Operating temperature-40 ~ 150℃ ←
Operating frequency 1~2500Hz←
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10-4
2. OPERATING FREQUENCY
1) Hydraulic and Electronic Control Unit (HECU)
Hydraulic and Electronic Control Unit (HECU) 1.
FL wheelRR wheelRL wheel
FR wheel
Master cylinder
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10-6
1. SYSTEM OVERVIEW
1) What is ABS?
When braking suddenly or braking on slippery roads, the vehicle keeps moving forward but the wheels
are locking and not rotating. If these happen, the vehicle may lose stability or rotate resulting in an
accident. ABS helps to maintain directional stability and control of the vehicle. ABS is designed to
secure more safety and increase the control of steering wheel during emergency braking situation. But,
ABS does not guarantee perfect safety beyond its physical limit. ABS in this vehicle contains EBD
function. In normal driving conditions, the brake system operates without ABS function.
2) What is EBD (Electronic Brake-force Distribution)?
EBD is an automobile brake technology that automatically varies the amount of force applied to each of a
vehicle's brakes, based on road conditions, speed, loading, etc. Always coupled with anti-lock braking
systems, EBD can apply more or less braking pressure to each wheel in order to maximize stopping
power whilst maintaining vehicular control. EBD does not operate when ABS is working.
ABS effect according to braking conditions ▶
Braking on split road Maneuvering while braking
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10-12
2) EBD (Electronic Brake-force Distribution) Warning Lamp
EBD warning lamps (brake warning lamp and ABS warning lamp) come on when the system performs
the self diagnosis and when it detects the malfunction of EBD system. However, the brake warning lamp
comes on regardless of EBD system when the parking brake is applied.
EBD warning lamp ON:
When turning the ignition switch to ON position, ABS warning lamp and the brake warning lamp
comes on for 3 seconds for self diagnosis and goes off if the system is OK (initialization mode).
When applying the parking brake, the brake warning lamp comes on.
When the brake fluid is not sufficient, the brake warning lamp comes on.
When disengaging the connector, the warning lamp comes on.
When the system is defective, ABS warning lamp and the brake warning lamp come on
simultaneously. A.
B.
C.
D.
E.
When the solenoid valve is defective
When one or more wheel sensors are defective
When ABS HECU is defective
When the voltage is abnormal
When valve relay is defective a.
b.
c.
d.
e.
When the communication between warning lamp CAN modules in meter cluster is failed, the
warning lamp comes on. F.
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10-134892-01
5. SYSTEM OPERATION
1) Block Diagram of ABS HECU
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2) DUMP (ABS is working) Mode
Even when the hydraulic pressure on each circuit is constant, the wheel can be locked as the wheel
speed decreases. This is when the ABS HECU detects the wheel speed and the vehicle speed and
gives the optimized braking without locking the wheels. In order to prevent the hydraulic pressure from
increasing, the inlet valve will be closed, the outlet valve will be opened and the oil will flow into the low
pressure chamber. In addition, the ABS HECU operates the pump to circulate the oil in the low pressure
chamber to the master cylinder. This may make the driver to feel the brake pedal vibration and some
Solenoid valve Valve Open/Close Pump motor
Inlet valve - Normal open (NO) valve Close
ON
Outlet valve - Normal close (NC) valve Open