Textbook

Module4 EPB (Electronic Parking Brake)

Module4 EPB (Electronic Parking
Brake)

4.1

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LESSON

Overview .............................................................................................................................99
4.1.1 Introduction....................................................................................................................... 99
4.1.2 Comparison of EPB Type ............................................................................................... 100

4.2

Layout ...............................................................................................................................101

Components .....................................................................................................................105
EPB Switch..................................................................................................................... 105
AVH Switch..................................................................................................................... 107
Clutch Sensor (M/T Vehicle)........................................................................................... 108
Neutral Switch (M/T Vehicle) .......................................................................................... 109

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4.3.1
4.3.2
4.3.3
4.3.4

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4.3

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4.2.1 Caliper Type ................................................................................................................... 101
4.2.2 Cable Type ..................................................................................................................... 103

4.3.5 EPB ECU (Caliper Type) ................................................................................................ 110
4.3.6 EPB Actuator (Caliper Type) .......................................................................................... 111

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4.3.7 EPB Unit (Cable Type) ................................................................................................... 112
4.3.8 EPB Lamp & AVH Lamp................................................................................................. 113
4.3.9 Cluster Message according to EPB, AVH ...................................................................... 114

Function............................................................................................................................115

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4.4


4.4.1 EPB Functions................................................................................................................ 115
4.4.2 AVH (Automatic Vehicle Hold) ........................................................................................ 116

4.5

Maintenance .....................................................................................................................117
Brake Pad Change (Caliper Type) ................................................................................. 117
BED-IN (Cable Type)...................................................................................................... 118
Post-Actuator Assembly Replacement Measures (Cable Type) .................................... 119
Troubleshooting when the EPB Cannot Be Released in Normal Procedures ................ 120

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4.5.1
4.5.2
4.5.3
4.5.4

[Learning Objectives]
▪ Explain the difference between the two types of EPB.
▪ Describe the system layout and list the locations, mechanisms and functions of components.
▪ Describe EPB's secondary functions and the purpose of AVH.
▪ Take the necessary measures after changing parts.

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Module4 EPB (Electronic Parking Brake)

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Module4 EPB (Electronic Parking Brake)

Overview

4.1.1

Introduction

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4.1

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EPB is an abbreviation of ‘Electronic Parking Brake’ system. Receiving the input signal (or at the time of
IG OFF automatically) from driver, the EPB control module will actuate the motor in order that the parking
brakes in rear both drums are engaged electrically.

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Interfacing with ESC control module via CAN, EPB controls not only parking brake but also hydraulic foot
brake in order to implement various functions and safety features such as AVH, DAR and DBF., etc. (it will
be explained more detail in the section of ‘Main function’)


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Comparing with the conventional mechanical type parking brake system, EPB has several benefits as
follows.
▪ More space and higher degree of design

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Due to the eliminated lever or pedal, possible to get more space for the passenger and to design with
various layout for the interior convenience device and can have more clean image as shown in the
picture.
▪ Automatic operation

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Without switch input, EPB engages the parking brake automatically as soon as the ignition off. In
addition, it is released automatically upon vehicle starting without switch input.
▪ AVH function

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Interfacing with ESC, the vehicle will not move backward when starts at the uphill road.
▪ Self diagnosis function
Due to the electronic control module and the interface with other control module via CAN, possible to
communicate with the scanner so that the system fault can be monitored in advance.

▪ Lowest braking effort

Using the electrical motor and cable, the minimum braking effort is required. The maximum pulling force
by motor is around 120kgf so that it is much more strong than the manual pulling force in the mechanical
parking system.
▪ Safety concept in emergency situation
In case of mechanical braking system, the parking brake cannot guarantee stable vehicle stop if foot
brake is failed. However, EPB offers much more stability for vehicle stop by controlling the cable
electronically (like ABS).

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Module4 EPB (Electronic Parking Brake)

4.1.2

Textbook

Comparison of EPB Type

EPB System is mainly divided into Caliper Type and Cable Type. Caliper Type: Electric motor integrated
with caliper pushes the caliper piston and engages the parking brake; Cable Type: Electric motor mounted
on the EPB actuator pulls on the parking cable and engages the parking brake.
Cable Type

Caliper Type

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Category

The system cost is high, noise is low.

Left & right disc brake

The electric motor integrated into the
caliper pushes the caliper piston for
operation.

Competitive in cost and installation
convenience.

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Advantages

The parking cable is pulled by the electric
motor for operation.


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Operation

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On the rear chassis module sub frame

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Actuator

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Module4 EPB (Electronic Parking Brake)

4.2

Layout

4.2.1

Caliper Type

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1) Overview

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Caliper type engages/releases parking brake by activating the EPB actuator by EPB ECU when signal is
received through the EPB Switch. The system is linked with ESC to automatically engage/disengage brake
(AVH) when a vehicle comes to a stop (traffic light). It prevents the vehicle from sliding backwards. EPB
also engages in an emergency situation for added safety.

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Module4 EPB (Electronic Parking Brake)

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2) In / Output Elements

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Configuration

Function

EPB switch gets driver’s intention. And it is connected to EPB ECU via
hard wire.

AVH Switch

Receives AVH activation signals (intention).
To perform drive away release function in a MT vehicle, clutch sensor input
is required. Clutch sensor is connected to EPB ECU via hard wire.


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Clutch Sensor (M/T)

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EPB Switch

Neutral Switch (M/T)
EPB ECU

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EPB Actuator

Receives various data and runs the EPB actuator.
Engages rear wheel brake.

Receives elevation data from the acceleration sensor and functions in
conjunction with EPB for automatic AVH.

ECM

Identifies engine RPM for reduced clamp force on flat and auto-apply when
engine turns off while AVH is on.

TCM

Supports drive away release and P/N to X based on gear shift data.


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ESC

Cluster

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To perform drive away release function in a MT vehicle, neutral sensor input
is required. neutral sensor is connected to EPB ECU via hard wire.

Dibased splays the EPB indicator and warning lamp; performs auto-adjust on
traveled distance data.

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4.2.2

Module4 EPB (Electronic Parking Brake)

Cable Type

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1) Overview

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Caliper type engages/releases parking brake by activating the EPB actuator by EPB ECU when signal
is received through the EPB Switch. The system is linked with ESC to automatically engage/disengage
brake (AVH) when a vehicle comes to a stop (traffic light). It prevents the vehicle from sliding backwards.
EPB also engages in an emergency situation for added safety.

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Module4 EPB (Electronic Parking Brake)


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2) In / Output Elements

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Configuration

Function

EPB switch gets driver’s intention. And it is connected to EPB ECU via
hard wire.

AVH Switch

Receives AVH activation signals (intention).
To perform drive away release function in a MT vehicle, clutch sensor input
is required. Clutch sensor is connected to EPB ECU via hard wire.

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Clutch Sensor (M/T)

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EPB Switch

Neutral Switch (M/T)

To perform drive away release function in a MT vehicle, neutral sensor input
is required. neutral sensor is connected to EPB ECU via hard wire.
EPB ECU and EPB actuator are integrated.

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EPB Unit

ESC

▪ EPB Actuator: Pulls the parking cable to generate brake force
Receives elevation data from the acceleration sensor and functions in
conjunction with EPB for automatic AVH.
Identifies engine RPM for reduced clamp force on flat and auto-apply when
engine turns off while AVH is on.

TCM

Supports drive away release and P/N to X based on gear shift data.

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ECM

Cluster

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▪ EPB ECU: Receives various data and runs the EPB actuator

Displays the EPB indicator and warning lamp; performs auto-adjust based on
traveled distance data.

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Module4 EPB (Electronic Parking Brake)

Components

4.3.1

EPB Switch

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4.3

Switch operation is as follows.

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The EPB switch receives the driver's intention to park. It is located on the floor console as shown in the
picture in the slide. Turning on the switch sends signals to EPB ECU. EPB Switch is connected via dual
circuit for enhanced system reliability. EPB actuator activates only when 2 contact signals are received.

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1 Pull switch within 3 seconds: Engages EPB with normal braking force
2 Pull switch for more than 3 seconds: Engages EPB with maximum braking force

In some 2012 and earlier models, EPB is engaged when the switch is pressed (like
the foot pedal), and EPB is released when the switch is pulled.

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NOTE

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3 Press switch once: Releases EPB

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Module4 EPB (Electronic Parking Brake)

Figure 4-1 EPB Switch Circuit (left) / EPB Switch Otput (right)

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▪ EPB State

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The time is a neutral state that a driver doesn’t operate EPB switch. If a driver pulls EPB switch to drive,
EPB switch enters apply state. Or if the driver pushes EPB switch to stop the vehicle, the state changes
to release state.
▪ EPB Switch Circuit


▪ EPB Switch Output

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EPB switch is composed of 4 pins. In ignition on, each switch pin receives voltage from EPB ECU at an
interval of 10ms pulse in every 40ms. The reason of using this kind of switch is to preventing sudden
operation. And when the driver operate the switch, the switch circuit is changed. And then the diode
direction is changed.

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As shown in the above diagram, the switch output voltage is dependent on diode direction, which is
set by the EPB switch state. Specifically, EPB ECU sends currents to the switch and switch output is
received for state recognition.

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4.3.2

Module4 EPB (Electronic Parking Brake)

AVH Switch

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AVH maintains ESC hydraulic pressure when the vehicle is parked. Releasing the brake pedal keeps the
vehicle stationary. AVH switch is a self-return type switch used to engage and disengage the feature.

▪ Press switch once: AVH on

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▪ Press switch once: AVH off

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Module4 EPB (Electronic Parking Brake)

4.3.3

Textbook

Clutch Sensor (M/T Vehicle)

The clutch sensor is applied on models with manual transmission and detects when the clutch pedal is
actuated. The signal is used for:
▪ Engine start (on models with smart key system)
▪ To switch off the cruise control system
▪ Reduce injection volume briefly for preventing engine jerk during shifting

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▪ For the drive away release function

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The clutch sensor contains two potentiometers. Both potentiometers receive power and ground from the
electronic parking brake control unit. When the clutch pedal is pressed, the lever mechanism is pushed
downward and rotates on the axis connected to the potentiometer. The corresponding signal is fed back
to the EPB control unit.

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Neutral Switch (M/T Vehicle)

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4.3.4

Module4 EPB (Electronic Parking Brake)

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The neutral switch identifies the current gear position. For the drive away release function, the neutral
switch is mounted on the transmission. The neutral switch has two pins. Pin number 1 is ground and 2 is
voltage in from ECM. In gear engagement switch open.

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Module4 EPB (Electronic Parking Brake)

EPB ECU (Caliper Type)

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4.3.5

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EPB ECU activates the EPB actuator after receiving signal from the EPB Switch, then enters various data

and engages additional functions, and controls the indication/warning lamp.

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EPB Actuator (Caliper Type)

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4.3.6

Module4 EPB (Electronic Parking Brake)

EPB actuator signifies the DC motor and the gear box installed in rear wheel caliper. The EPB caliper is
made up of a hydraulic device and motor. The hydraulic device is used for normal braking, while the motor
is used for parking.

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First, DC motor can be rotated by DC power from EPB ECU. And then gears, spindle are rotated. And nut
spindle goes ahead with piston. As a result brake pad can compress disc brake

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Module4 EPB (Electronic Parking Brake)

EPB Unit (Cable Type)

Figure 4-2 Rear Suspension Frame

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4.3.7

Textbook


EPB Unit signifies the entire module integrated with EPB ECU and EPB actuator. so that it must be replaced
with assembly.

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EPB ECU activates the EPB actuator after receiving signal from the EPB Switch, then enters various data
and engages additional functions, and controls the indication/warning lamp.

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The EPB actuator is made up of a weight sensor, parking cable, DC motor and gearbox (deceleration gear).
The force sensor that using piezo effect is built in the assembly to measure the tension force directly acting
on the cable. In order to minimize the operating noise, the plastic helical gear has been applied in the gear
box. No position sensor is applied in the motor.

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When DC motor activates by EPB signal, the gear rotates and spins the bolt screw. This spins the
connected nut screw, and activates the parking brake in DIH.

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Due to the independent battery power supply to EPB control module, it is possible to engage in IG off
condition.

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Figure 4-3 Actuator Structure

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Module4 EPB (Electronic Parking Brake)

EPB Lamp & AVH Lamp

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4.3.8

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ESC ECU engages Indicator Lamp/Warning Lamp control to check operation status of EPB systems and
alerts the driver in case of malfunction. All the Indicator Lamps/Warning Lamps are turned ON for 3 seconds
when switched to IG ON Mode or when the engine is started. This is a self-diagnosis process. If all the

system is normal, the warning lamps turn OFF. If any of the lamps remain turned ON, it signifies failure of
the corresponding system.

1) EPB Lamp

EPB Failure

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EPB Switch Active

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EPB Warning Lamp

EPB Switch Inactive

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Category

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If EPB Switch is pulled while the vehicle is stopped, the EPB brake is engaged and brake warning lamp is
turned ON. Then if EPB Switch is pressed, the EPB is released and the brake warning lamp is turned OFF.
EPB warning lamp comes ON (green) only while EPB Switch is engaged, and EPB warning lamp changes
color (from green to white) when the switch is released. If the brake warning lamp remains ON even after
EPB is completely released, then it is due to EPB system malfunction. In such a case, yellow EPB warning
lamp is turned ON.


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2) AVH Lamp

Category

AVH Standby

AVH Active

AVH Failure

AVH Warning Lamp

AVH is the function that holds the vehicle with hydraulic brake after coming to a stop even when the brake
pedal is released. When the function is in standby mode while driving, the AVH lamp is white. When it is
active, it is green, and in case of failure, yellow AVH lamp is turned ON. When AVH function is disabled,
the AVH warning lamp is turned OFF.

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Module4 EPB (Electronic Parking Brake)

4.3.9


Textbook

Cluster Message according to EPB, AVH

EPB and AVH system status and data are displayed on the cluster LCD. Displayed items are as follows.

Image

Category

Warning
Sound

Meaning

If the AVH is turned OFF by using
the AVH switch, the message is
indicated to inform the driver that
the Auto Hold is disengaged only
by pressing the brake pedal for
safety reason.

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Press the
brake pedal to
disengage the
Auto Hold.


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When the activation condition for
DAR (Drive Away Release) for the
parking brake force is met.
EPB Auto Release
Not Possible

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▪ Activation Conditions
• IG ON

Warning alert
sounds 1 time

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• Safety belt fastened

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Parking brake
is automatically
engaged.

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• Door, trunk, and hood are
closed.

Press the
brake pedal to
disengage the
Auto Hold.

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When the auto-switch conditions
from AVH to EPB are met.
▪ Conditions for Lamp ON
• When the AVH has been
activated for more than 10
minutes.

Warning alert
sounds 1 time

• When the AVH is activated on
the gradient of 25% or more.
• When the AVH malfunctions

When the auto-switch conditions
from AVH to EPB arise.
▪ Conditions for Lamp ON
• After the AVH is released due
to the EPB failure while the
AVH is activated, the EPB
activation linkage is broken so
the system alerts the driver to
use the brake.

Warning
alert sounds
continuously

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Module4 EPB (Electronic Parking Brake)

4.4

Function

4.4.1

EPB Functions

EPB System includes various auxiliary functions for enhanced driver convenience, and improved safety

during emergency situation by incorporating ESC functions.

Static Apply

Function

While stationary, manually control (pull) the EPB
switch to engage the parking brake.

While stationary, manually control (press) the EPB
switch to release the parking brake.

Auto Apply

Automatically engages parking brake without switch
control.

Drive Away Release

Automatically releases parking brake without switch
control.

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Static Release

Controls the parking brake force corresponding to the
incline of the road.


Electric Controlled
Deceleration

Hydraulic brake is applied for the duration of holding
down the EPB switch in an emergency situation (linked
with ESC).

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In case of vehicles without ESC, or in case of ESC
failure, deceleration is achieved by activating the
actuator when EPB switch is pulled.

If vehicle speed data is not available due to system
failure, the vehicle stopped state is determined through
acceleration sensor signal and EPB is activated.

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Dynamic Standstill
Detection

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Reduced Clamp Force
on Flat

Rear Wheel Unlocker


Remarks

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Item

Roll Away Reclamp

If vehicle slide is detected while EPB is engaged, EPB
is activated again for increased brake force.
Shifting the gear from P or N to D or R automatically
releases parking brake force.

External Apply

ESC command automatically converts AVH to EPB.

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P to X, N to X

Releases EPB by system request.

CALIPER TYPE

Auto Adjust

Increases EPB engagement time to compensate for

worn-out brake pads.

CALIPER TYPE

High Temperature
Reclamp

Re-engages EPB after a set time to address reduced
brake force caused by overheating.

CALIPER TYPE

Pad Change Mode

Moves the caliper piston backwards to facilitate
changing of rear wheel brake pad.

CALIPER TYPE

Regular inspection (brake force inspection) performed
on a roller bench

CALIPER TYPE

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External Release

HU Function


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Module4 EPB (Electronic Parking Brake)

4.4.2

Textbook

AVH (Automatic Vehicle Hold)

② Vehicle is maintained
in stopped position

③ Accel pedal is
engage

④ Vehicle starts to
move

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① Brake pedal is
released after coming
to full stop

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1) Overview

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Automatic Vehicle Hold (AVH) is a feature that maintains the vehicle at stopped state even when the driver
releases the brake pedal after coming to a stop when in D/R/N or in Sports Mode. Brake is automatically
released when taking off by pressing the accel pedal while in D/R or in Sport Mode.

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2) Mechanism

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With the AVH switch on stand-by, press the brake pedal to keep the vehicle stationary. Cut off the brake
fluid in which the N/O solenoid valve inside HCU is restored when the brake pedal is released to keep the
brakes applied.

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Module4 EPB (Electronic Parking Brake)

4.5

Maintenance

4.5.1

Brake Pad Change (Caliper Type)

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1) Purpose

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Brake pad change is required when a worn-out brake pad in a caliper-type EPB requires changing.

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Use GDS to create space for a new pad.


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① Worn-out pad

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2) Procedure

② Retracts the nut spindle

③ Replace with a new pad
(using GDS)

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1 When the brake pads are worn out, the piston in caliper moved to front brake pad. To change worn
brake pads, you should be performed brake pad change mode in GDS.
2 In this situation, to arrange new pad’s installation space, this mode should be performed to back
nut spindle.

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3 And after separating the caliper from the rear wheel, push the piston into caliper.
4 Then you can change brake pads.
5 Repeat apply/release three times after a pad change.


3) Precautions
When changing brake pads in pad change mode, assemble the EPB caliper in the correct location and
ensure the hand is not between the pad and disk before exiting pad change mode. Failing to follow the
above safety precaution may lead to an injury. In addition, if the brake pedal is pressed while the brake
pad is removed, or Lining Change mode is selected with the diagnostic device (after pad replacement), the
spindle may move forward since the caliper piston might be pushed outside or the EPB is engaged.

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Module4 EPB (Electronic Parking Brake)

4.5.2

Textbook

BED-IN (Cable Type)

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1) Purpose

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The gap between the brake drum and lining is very important in the cable type EPB System. If this gap is
excessively wide, then that much more cable needs to be pulled when the EPB is engaged, and may result

in the damage of the cable inside the actuator.

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After the gap adjustment, in order to increase the friction forces in the drum and the lining, the BED-IN
work should be performed.

2) Procedure
Entering BED-IN Mode

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●

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a After the engine starts while holding down the brake pedal when the vehicle is stopped, operate the
brake pedal twice within 10 seconds; for the second time, keep the pedal pushed down (activate
→ release → maintain activation).
b Within 10 sec with the pedal held down, pull the EPB switch 4 times in a row (activation direction),
and right in succession press 3 times in a row.

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c Vehicle enters the BED-IN Mode when the above procedure is complete.
d To return to Normal Mode from the BED-IN Mode, drive the vehicle at speed over 50km/h or
turn the engine OFF.

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e To check if the vehicle has entered BED-IN mode, drive at a speed less than 50km/h and activate
(pull) the EPB switch. BED-IN mode is enabled if the parking brake lamp blinks on the cluster.
BED-IN Procedures

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a In BED-IN mode, keep a speed of 30-35km/h and pull the EPB switch and keep it activated until
the speed reaches 0km/h.
b Drive 500m (at lower than 50km/h) without activating the EPB switch or cool down for 1 minute
while stationary.
c Repeat 1 to 2 five times.
d End BED-IN mode by turning the engine off.

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4.5.3

Module4 EPB (Electronic Parking Brake)

Post-Actuator Assembly Replacement
Measures (Cable Type)


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A new replacement EPB actuator assembly manufactured by Hyundai Mobis comes with the parking cable
maximally released. Install the assembly on the member, connect the end of the parking cable to the lining
hook on DIH and activate the EPB switch to adjust the cable tension (no other adjustment is required).

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Module4 EPB (Electronic Parking Brake)

Troubleshooting when the EPB Cannot Be
Released in Normal Procedures

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4.5.4

Textbook

1 In case of battery discharge, jump-charge the battery then release the EPB via EPB Switch.

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2 For the cable-type, if the cable has been chewed, use the switch and diagnostic equipment to release
EPB and have the drum-lining clearance inspected and adjusted at a repair shop.
3 Towing is required if ECU, motor or cable fault occurs with the parking brake engaged.

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4 For the cable-type, having the actuator replaced requires cable removal/replacement after DIH
clearance adjustment. For the caliper-type, activate and disable the actuator by force using a hex key
before repairs.

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