ECU SSANGYONG TURISMO 2013 Repair Manual

09-10
Pressure Sensor
InstalledRemoved
2. LAYOUT
HECU (Hydraulic &
Electronic Control Unit)
ESP ABS
Front Wheel Speed Sensor
4WD 2WDRear Wheel Speed
Sensor
1) Exterior Components

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(3) ESP Control
The ESP (Electronic Stability Program) has been developed to help a driver avoid danger of losing
control of the vehicle stability due to understeer or oversteer during cornering. The yaw rate sensor,
lateral sensor and longitudinal sensor in the sensor cluster and the steering wheel angle sensor under
the steering column detect the vehicle conditions when the inner or outer wheels are spinning during
oversteer, understeer or cornering. The ESP ECU controls against oversteer or understeer during
cornering by controlling the vehicle stability using input values from these sensors and applying the
braking force to the corresponding wheels independently. The system also controls the engine power
right before the wheel spin synchronized to decelerate the vehicle automatically in order to maintain the
vehicle stable during cornering.

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3) 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.

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(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.

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(2) Hydraulic Circuit of HBA
The above figure shows one front and one rear wheel and the same hydraulic circuit forms as in the
ESP operation. When HECU recognizes that it is an emergency and it is required for hard braking,
depending on the pressure value of the brake pressure sensor and pressure changes caused by the
pressure sensor timing, it operates the pump immediately to apply the brake pressure at the wheels.
Then, the pressure in the pump increases until just before the corresponding wheel gets locked. The
motor still keeps rotating and the outlet valve and the separation valve will stay closed. When the wheel
starts to lock, the HBA function cancels and switches to ABS operation.

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â–¶DUMP (ESP is working) Mode
The pressure decreases just before the wheel speed drops and the wheels are locked.
The inlet valve closes and the outlet valve opens as in the ESP HECU and the oil is gathered at the
low pressure chamber while no additional oil is being supplied. Then the pump operates to allow fast oil
drainage. The shuttle valve and the separation valve do not operate while decompression.

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1. SYSTEM OVERVIEW
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.
1) Basic Theory of ABS Function
To give you a better understanding of the tasks and functions of ABS, we will first look at the physics
principles.
â–¶Stopping distance
The stopping distance depends on the vehicle weight and initial speed when braking starts. This also
applies for vehicle with ABS, where ABS always tries to set an optimum brake force on each wheel. As
great forces are exerted between the tires and the carriageway when braking, even with ABS the
wheels may scream and rubber is left on the road. With an ABS skid mark one may be able to clearly
recognize the tire profile. The skid mark of an ABS vehicle does not however leave any hint of the
speed of the vehicle in the case of an accident, as it can only be clearly drawn at the start of braking.
â–¶Brake force on a wheel
The maximum possible brake force on a wheel depends on the wheel load and the adhesion
coefficient between tire and carriageway. With a low adhesion coefficient the brake force, which can be
obtained is very low. You are bound to know the result already from driving on winter roads. With a
high adhesion coefficient on a dry road, the brake force, which can be obtained, is considerably higher.
The brake force, which can be obtained, can be calculated from below formula:

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Warning Lamps
EBD warning lamp ABS warning lamp
2. COMPONENTS AND LAYOUT
The basic functions of ABS system are same with previous version. However, the wheel speed
sensing type is different from previous version.
For details about the components,
refer to Chapter "ESP".
Front Active Wheel Speed Sensor
4WD 2WD
ABS HECU
Rear Active Wheel
Speed Sensor

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2) EBD (Electronic Brake Force Distribution) System
â–¶System description
As an add-on logic to the ABS base algorithm, EBD works in a range in which the intervention
thresholds for ABS control are not reached yet.
EBD ensures that the rear wheels are sensitively monitored for slip with respect to the front axle. If slip
is detected, the inlet valves for the rear wheels are switched to pressure hold to prevent a further
increase in pressure at the rear-wheel breaks, thus electronically reproducing
a pressure-reduction function at the rear-wheel brakes.
ABS features an enhanced algorithm which includes control of the brake force distribution between the
front and rear axles. This is called Electronic Brake Distribution. In an unloading car condition the brake
efficiency is comparable to the conventional system but for a fully loaded vehicle the efficiency of the
EBD system is higher due to the better use of rear axle braking capability.
â–¶Advantages
Elimination of conventional proportioning valve EBD utilizes the existing rear axle wheel speed
sensor to monitor rear wheel slip.
Based on many variables in algorithm a pressure hold, increase and/or decrease pulsetrain may
be triggered at the rear wheels insuring vehicle stability.
Vehicle approaches the ideal brake force distribution (front to rear).
Constant brake force distribution during vehicle lifetime.
EBD function is monitored via ABS safety logic (conventional proportioning valves are not
monitorable). -
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3) Important Notice
The modulators for production line are not filled with the brake fluid (dry type). But, for after service, they
are filled with the brake fluid (wet type).
Make sure to keep the procedures in service manual when bleeding the air from the brake lines.
Be familiar with the lamp ON conditions to provide the correct information and reliability to customers.
ECU monitors the valve and motor for ABS when the vehicle speed approaches 5 km/h. At this time,
you can hear the clattering noise. 1.
2.
3.

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â–¶Pressure Decreases in the Circuit when ABS is Operating
Even when the hydraulic pressure on each circuit is stable, the wheel can be locked as the wheel
speed decreases. This is when the ABS ECU detects the wheel speed and the vehicle speed and
gives the optimized braking without locking the wheels. In order to prevent from hydraulic pressure
increases, the inlet valve is closed and the outlet valve is opened. Also, the oil is sent to the low
pressure changer and the wheel speed increases again. The ABS ECU 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.
â–¶Pressure Increases in the Circuit when ABS is Operating
As the wheel speed increases, the inlet valve opens and the wheel’s pressure increases due to
the master cylinder pressure. The oil in the low pressure chamber circulates to the wheel by the pump
and the wheel speed decreases as the hydraulic pressure at wheel increases. This operation
continues repetitively until there are no signs that the ECU is locking the wheels. When the ABS
hydraulic pressure control takes place, there may be some vibration and noises at the brake pedal.