ECU SSANGYONG RODIUS 2012 Repair Manual

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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 ABS 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
<0068009a0047009b008f008c0047009e008f008c008c00930047009a0097008c008c008b004700900095008a0099008c0088009a008c009a00530047009b008f008c0047009000950093008c009b0047009d00880093009d008c004700960097008c009500
9a004700880095008b0047009b008f008c0047009e008f008c>el’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.

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Rear air conditioner module assembly - bottom of rear left
Engine ECU - passenger's
footstep
CondenserRecevier driver-condenser
right
Rear fan speed dial
Sub-condenser - right wheel
front
Absorbs moisture in the
refrigerant and reserves
refrigerant to supply
smoothly. *Instslled in front of vehicle and
condenses vapor refrigerant into
low temperature and high
pressure liquid refrigerant *
Condenses high temperature and
high pressure vapor refrigerant into
low-temperature-high-pressure
liquid refrigerant. *
Detects A/C AUTO switch position,
coolant temperature, engine
condition and driving condition to
control the air conditioner *
A sensor that detects coolant
temperature and transmits to
engine ECU *
Blower motor
Power transistor
Air conditoner high
pressure/low
pressure pipe
Air mix door
actuator
Front
Rear
A switch that controls the rear air
conditioner module. *
Collant temperature sensor -
on engine