Page 950 of 1082
10-194890-00
6. HYDRAULIC CIRCUIT OF ABS
1) Normal Brake Operation (ABS is not working) Mode
If the driver depress the brake pedal so that the ABS does not operate, the hydraulic pressure in the
master cylinder increases through the vacuum booster and it is delivered to the wheel via the normal
open inlet valve. At this moment, the normally-closed outlet valve is closed The speed of the wheel that
hydraulic pressure is delivered reduces gradually.
Solenoid valve Valve Open/Close Pump motor
Inlet valve - Normal open (NO) valve Open
OFF
Outlet valve - Normal close (NC) valve Close
Page 951 of 1082
10-20
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
noises.
Solenoid valve Valve Open/Close Pump motor
Inlet valve - Normal open (NO) valve Close
ON
Outlet valve - Normal close (NC) valve Open
Page 953 of 1082
10-22
4) RISE (ABS is working) Mode
As the wheel speed increases, the inlet valve opens and the wheel's pressure increases due to the
master cylinder pressure. In addition, the pump circulates the oil in the low pressure chamber to the
wheel. As the hydraulic pressure to the wheel increases, the wheel speed will reduce. This operation
continues repetitively until there are no signs that the ABS HECU tends to lock the wheels. Since the
ABS hydraulic pressure control process takes place repeatedly for a short time, there may be some
vibration and noises at the brake pedal.
Solenoid valve Valve Open/Close Pump motor
Inlet valve - Normal open (NO) valve Open
ON
Outlet valve - Normal close (NC) valve Close
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11-8
3. PRECAUTIONS
The warning lamp flashes and warning beep sounds when the ESP is operating
When the ESP operates during vehicle movement, the ESP warning lamp on the instrument panel
flashes and beep comes on every 0.1 second. The ESP system is only a supplementary device for
comfortable driving. When the vehicle exceeds its physical limits, it cannot be controlled.
Do not rely on the system. Keep on the safe driving.
Feeling when ESP is working
When the ESP system activates, the feeling can be different depending on vehicle driving conditions.
For example, you will feel differently when the ESP system is activated during the ABS is operating
with the brakes applied and when the brakes are not applied on a curve.
If the ESP system operates when the brake is applied, the brake pressure will be increased on the
corresponding wheel which already has braking pressure for the ESP controls.
ARP Operation
During the ARP operation, vehicle safety (rollover prevention) takes the first priority and thus,
stronger engine control is in effect. Consequently, the vehicle speed decreases rapidly, so the driver
must take caution for the vehicle may drift away from the lane.
Noise and vibration that driver feels when ESP system is operating
The ESP system may transfer noise and vibration to the driver due to the pressure changes caused
by the motor and valve operations in a very short period of time. And, keep in mind that the output
and vehicle speed could be decreased without rpm increase due to the ASR function that controls
the engine power.
Page 961 of 1082
11-90000-00
4. WARNING LAMPS
1) ABS
ABS warning lamp module indicates the self-diagnosis and malfunction.
ABS warning lamp ON: Warning Lamp
When turning the ignition switch to ON position, ABS warning lamp comes on for 3 seconds for self-
diagnosis and goes off if the system is OK (initialization mode).
When the system is defective, the warning lamp comes on.
When the self-diagnosis is performing, the warning lamp comes on.
When the HECU connector is disconnected, the warning lamp comes on.
ABS is not available during lamp ON. In this condition, Only normal brake system without ABS
function is available.
When the communication between warning lamp CAN module in meter cluster, the warning lamp
comes on. 1.
2.
3.
4.
5.
6.ABS warning lamp
Brake warning lamp
ESP OFF indicator
ESP warning lamp/indicator
EBD warning lamp 1.
2.
3.
4.
5.
Page 962 of 1082

11-10
2) EBD (Electronic Brake-force Distribution) Warning Lamp (Brake
Warning Lamp)
EBD warning lamp when the system perform the self diagnosis and when it detects the malfunction of
EBD system. However, the brake warning lamp comes on regardless of EBD 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 the self-diagnosis is performing, the warning lamp comes on.
When the HECU connector is disconnected, the warning lamp comes on.
When the system is defective, ABS warning lamp and the brake warning lamp come on
simultaneously. 1.
2.
3.
4.
5.
6.
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 module in meter cluster, the warning lamp
comes on. 7.
3) ESP OFF Indicator
ESP OFF indicator ON:
When turning the ignition switch to ON position, ESP warning lamp comes on for 3 seconds for self
diagnosis and goes off if the system is OK (initialization mode).
When the ESP OFF switch is pressed to turn off ESP function, ESP OFF indicator comes on. 1.
2.
4) ESP Warning Lamp
ESP warning lamp ON:
When turning the ignition switch to ON position, ESP warning lamp comes on for 3 seconds for self
diagnosis and goes off if the system is OK (initialization mode).
When the system is defective, the warning lamp comes on.
When the ESP function is activated, ESP warning lamp blinks with the interval of 2 Hz.
When the communication between warning lamp CAN module in meter cluster, the warning lamp
comes on. 1.
2.
3.
4.
5.
5) ESP OFF Switch
If ESP OFF switch is pressed, ESP function is deactivated and the ESP OFF indicator in the instrument
cluster comes on.
To resume the ESP function, press the switch again. At this time, ESP OFF indicator goes out.
Page 966 of 1082
11-14
3) Vehicle Control During Cornering
The figure below shows the vehicle controls by the ESP system under various situations such as when
the brake pedal is depressed or not depressed during cornering, when the ABS is operating and when
braking without the ABS. It also includes the vehicle conditions when the TCS, a part of the ESP system,
is operating.
Condition Understeer control Oversteer control
Only ESP in
operation
No braking by driver
ESP
+
Normal braking
(no ABS operation)
ESP
+
ABS brake
ESP + ASR
Page 967 of 1082

11-150000-00
4) HBA (Hydraulic Brake Assist System)
(1) Purpose
HBA (Hydraulic Brake Assist) system helps in an emergency braking situation when the driver applies
the brake fast, but not with sufficient pressure, which leads to dangerously long braking distance. ECU
recognizes the attempt at full braking and transmits the signal calling for full brake pressure from the
hydraulic booster. An inexperienced, elderly or physically weak driver may suffer from the accident by not
fully pressing the brake pedal when hard braking is required under emergency. The HBA System
increases the braking force under urgent situations to enhance the inputted braking force from the driver.
Based on the fact that some drivers depress the brake pedal too soft even under when hard braking is
necessary, the HECU system is a safety supplementary system that builds high braking force during
initial braking according to pressure value of the brake pressure sensor and the pressure changes of the
pressure sensor intervals. When the system is designed to apply high braking force when brake pedal is
depressed softly by an elderly or physically weak driver, the vehicle will make abrupt stopping under
normal braking situation due to high braking pressure at each wheels.
(2) Operation
The brake pressure value and the changed value of the pressure sensor are the conditions in which the
HBA System operates. There are 2 pressure sensors under the master cylinder. When the ESP ECU
system determines that emergency braking is present, the pump operates, the brake fluid in the master
cylinder is sent to the pump and the braking pressure is delivered to the wheels via the inlet valves . If the
drive depress the brake pedal slowly, the pressure change is not high. In this case, only the conventional
brake system with booster is activated.
(3) Operating conditions
Sensor pressure: over 40 bar
Pressure changes: over 850 bar/sec
Vehicle speed: over 30 km/h -
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