Textbook

Module6 ECS (Electronic Control Suspension)

Module6 ECS (Electronic Control
Suspension)

6.1

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LESSON

Overview ...........................................................................................................................145
6.1.1 Introduction..................................................................................................................... 145
6.1.2 History ............................................................................................................................ 146

Electronic Control Suspension ......................................................................................147

6.3

Overview ........................................................................................................................ 147
Layout............................................................................................................................. 148
Components ................................................................................................................... 149
Control............................................................................................................................ 152

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6.2.1

6.2.2
6.2.3
6.2.4

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6.2

Electronic Control Air Suspension ................................................................................155

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6.3.1 Overview ........................................................................................................................ 155
6.3.2 Layout............................................................................................................................. 156
6.3.3 Components ................................................................................................................... 157
6.3.4 Control............................................................................................................................ 162

Cautionary Measures for Handling Different Parts ......................................................... 167
Air Filling......................................................................................................................... 169
Maintenance Measures by Case.................................................................................... 171
Cautionary Measures for Lift-up (Iinitialized Vehicles) ................................................... 172
Cautionary Measures for Towing.................................................................................... 173

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6.4.1
6.4.2

6.4.3
6.4.4
6.4.5

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Maintenance (for ECAS) ..................................................................................................167

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6.4

[Learning Objective]

▪ Describe the history of ECS and different types of control.
▪ Describe the system layout and list the locations, mechanisms and functions of components.
▪ Create a pneumatic circuit for vehicle height control by ECAS.
▪ Take necessary actions after a part change and list the cautionary measures required for
maintenance.

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Module6 ECS (Electronic Control Suspension)

6.1


Overview

6.1.1

Introduction

Electronic Control Suspension (ECS) was developed to provide consistent ride comfort and driving stability
in various driving conditions.

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A suspension system is designed to support vehicle weight for improved ride comfort and driving stability.
It improves the tire-surface traction of a vehicle being driven and absorbs vehicle body vibration and impact
caused by surface contact.

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However, suspension systems cannot guarantee both ride comfort and driving stability as their spring
constant and shock absorber damping force are given a certain setting. For example, a lower spring
constant is used for a smoother and more comfortable ride, but this results in increased spring movement
from environmental elements as well as the movement of the vehicle itself. For this reason, a lower spring
constant's driving stability is reduced by high speeds and uneven surfaces.

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ECS addresses this issue by reducing a suspension's damping force for ride comfort in normal driving
conditions and increasing the damping force when driving on uneven surfaces and at high speeds for
driving stability. In short, ECS varies spring constant, shock absorber damping force and air spring circuit
pressure according to driving speeds and road conditions to control vehicle height/position for improved
driving stability and ride comfort.

Conventional Suspension System

ECS (Electric Control Suspension)

Cannot provide both ride comfort and
driving stability

Controlled to suit different driving conditions for
both ride comfort and driving stability

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Module6 ECS (Electronic Control Suspension)

6.1.2

Textbook

History

There are two types of ECS: Electronic Control Suspension and Electronic Control Air Suspension.
ECS controls damping force and is generally found in mid-size passenger vehicles. By adjusting the oil
flow inside the shock absorbers, ECU controls the shock absorber damping force according to vehicle
movement to produce vehicle movement that is optimum for given driving conditions.

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ECAS controls damping force and vehicle height, and is generally found in luxury passenger vehicles. Its
components include a variable damper, for damping force control, and a length-adjustable air spring. The
air spring ensures driving stability by keeping the position of an accelerating, braking or cornering vehicle
horizontal. High-frequency vibrations that coil springs cannot absorb are absorbed by air springs, which
results in ride comfort. As such, vehicle-height-controlling suspension systems are ideal as they provide
both ride comfort and driving stability.

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Module6 ECS (Electronic Control Suspension)

6.2

Electronic Control Suspension

6.2.1

Overview

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ECS controls a vehicle's damping force in real-time according to the driver's settings and driving conditions
for optimum ride comfort and enhanced driving stability. The damping force of the shock absorbers installed
on a vehicle's four wheels are adjusted to an optimum level by ECU to keep the vehicle as level with the
ground as possible at all times.

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In older-model vehicles, damping force was controlled in three stages; in late-model vehicles, non-staged
precision control of damping force is achieved through variable dampers.

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Layout

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6.2.2

Textbook

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Damping-force-controlling ECS continuously adjust each wheel's damping force through continuously

variable dampers to produce optimum vehicle movement. It receives signals from the body G sensor
(detects vehicle movement), wheel G sensor, steering angle sensor (detects the driver's intentions),
speed sensor and TPS to identify the driving conditions. Damping-force-controlling ECS components
include an ECS mode switch, for enabling damping force control mode, and ECS lamp, which indicates
system troubles and ECS mode.

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6.2.3

Module6 ECS (Electronic Control Suspension)

Components

1) Continuously Variable Damper
1 Functions and Roles

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Made up of an integrated shock absorber and solenoid valve, a continuously variable damper is
installed on each of a vehicle's four wheels. Solenoid valve control allows damping force (force that
tries to stop spring movement against the shock absorber) to be continuously controlled.

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2 Mechanism

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ECS ECU controls the damping force variable solenoid valve according to driving conditions. Current
control moves the spool valve inside the solenoid valve to change the flow and continuously switch
the damping force of the continuously variable damper.

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An electrical current between 0.3-1.3 A is needed for the external solenoid valve. Current adjustment
to 0.3A moves the spool valve up and constricts the orifice, slowing down oil flow and increasing
damping force; this "hardens" the ride feel (hard mode). Conversely, current adjustment to 1.3A moves
the spool valve down and expands the orifice, speeding up oil flow and decreasing damping force; this
"softens" the ride feel (soft mode).

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2) Body G Sensor

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The body G sensor measures vehicle acceleration at the top and bottom to detect upper/lower vehicle body
movement. It provides the main signals used in anti-bounce, anti-pitch and anti-roll control. Detection of
movement on a flat surface requires at least three sensors; two G sensors are installed in the engine room
and another on the trunk left panel. If the body acceleration sensors are mounted at just the front and rear,
surface changes are harder to detect, which leads to a reduction in vehicle control. The sensors must be
installed with the arrow pointing down toward the surface.

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3) Wheel G Sensor

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4) SAS (Steering Angle Sensor)


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Installed under the continuously variable damper of the front wheels, the wheel G sensor detects tire
operation and continuously variable damper speed in harsh conditions mode. It can detect the surface
quality of unpaved roads and the rough conditions of uneven surfaces. Compared to conventional versions,
the damper is precisely controlled to improve ride comfort as the vehicle passes over uneven road surfaces.

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The steering angle sensor detects steering speed and angle to detect vehicle body roll. It provides the
input signals required for anti-roll control. This sensor is installed inside the MDPS assembly and receives
signals through CAN communication with MDPS.

5) WSS (Wheel Speed Sensor)

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The wheel speed sensor detects wheel speed to provide the input signals required for handling, anti-squat
and high-speed stability control. It uses a hall element and is installed on the tone wheel, and receives
signals through CAN communication with ECS/ABS.

Wheel G Sensor

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SAS (Steering Angle Sensor)


WSS (Wheel Speed
Sensor)

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Module6 ECS (Electronic Control Suspension)

6) ECS Mode Switch

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Figure 6-1 ECS Switch

The ECS mode switch (self-return-type) is used by the driver to switch between sport mode and normal
mode to suit driving conditions. A single press enables sport mode and another single press enables auto
mode.

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Sport mode puts CDC in "hard mode" to improve driving stability at the expense of ride comfort for driving
through multiple bends and sporty driving.

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7) ECS ECU

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ECS ECU is installed on the right of the center of the cowl crossbar. With vehicle driving/position data
received from various sensors, ECS ECU performs real-time solenoid valve control for adjustment of the
damping force of the variable dampers installed a vehicle's four wheels.

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ESC ECU operation is controlled by the actuator relay located at the center of the dash panel. Upon
activation, the actuator relay supplies currents to the damping force variable solenoid vagve through the
ECU's internal circuit. If engine RPM falls below 500 while driving, ECU stops actuator relay operation.

8) ECS Lamp
Located on the cluster, the ECS indicator switches on when sport mode is selected, blinks when ECS is
faulty and switches off in normal mode. Contacts are controlled according to ECU switch signals or in the
event of ECU trouble.

Figure 6-2 ECS Lamp

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6.2.4

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Control

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1) Input & Output Elements

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2) System Control

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Power-supply to ECS ECU triggers ECU to inspect components and prepare for operation. The body
G sensor and wheel G sensor detect vehicle movement and send data to ECU. The driver's intentions
are detected through the ECS mode switch, vehicle speed, throttle position sensor, brakes and steering
angle sensor; after required damping force control is calculated, the damping force variable solenoid is
controlled. When sport mode is enabled, the ECS indicator switches on. In the event of system trouble,
the ECS warning lamp blinks and communication takes place with external diagnostic equipment for trouble
diagnosis.

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Item

Ride control logic
(pitch, bounce)

Description

Input Element

Top/bottom vibration
suppression when
driving on an inflected
surface

Body G Sensor (3EA)


Control

Wheel G sensor (2EA)
ECS mode switch
Road Detection →
Skyhook Control

Left/right vibration
suppression during
turns

Steering Angle Sensor
ECS mode switch

Anti-roll control logic

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Module6 ECS (Electronic Control Suspension)
Item

Description

Input Element


Front/rear vibration
suppression in braking

Wheel Speed Sensor

Control

Brake switch

Anti-dive control logic

TPS

Improved driving
stability in high-speed
driving

ECS mode switch

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Anti-squat control logic

Speed sensitive
control logic

Solenoid Control (4EA)
→ Switch to hard
damping force


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Front/rear vibration
suppression in sudden
start-offs

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3) Skyhook

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The damper is connected to an imaginary atmosphere to minimize body vibration. Skyhook control takes
place automatically when pitch, bounce or roll occurs. Based on body and wheel acceleration, skyhook
improves ride comfort and driving stability through continuous damping force control.

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Module6 ECS (Electronic Control Suspension)

6.3

Electronic Control Air Suspension

6.3.1

Overview

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ECAS uses air to maintain a consistent vehicle position against vehicle load changes and uses variable
dampers to perform non-staged damping force control (hard/soft). It is a system that provides greatly
improved ride comfort and driving stability. The air springs applied to damping control in place of the
conventional coil springs enable vehicle height adjustment through air supply/discharge.
The following change occurred for further-improved response and driving stability.
Item

Past
▪ Open Loop

▪ Open Loop


▪ 4 Corner

▪ 4 Corner

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System

Current

Response Time
21 - 26 sec

2.5 - 4.5 sec

Damper Damping
Force Adjustment

Low, Normal, High, EX-High

Low, Normal, High

Step Motor installation

External solenoid

▪ (coil) + air spring

▪ Individual air spring installation


▪ 6-bar internal pressure (slow
vehicle height adjustment)

▪ 10-bar internal pressure (fast
vehicle height adjustment)

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Air Spring

Non-staged control

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Vehicle Height
Control Mode

Soft, Auto Soft, Medium, Hard

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Damping Force Mode

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(down by 25mm)

▪ Aluminum-guide-attached


Air-supply

Open Loop System (slow response)

Closed Loop System (fast response)

Vehicle Height
Adjustment

Highway and rough driving function

Highway and rough driving function

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▪ No guide

Spring Shape

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Module6 ECS (Electronic Control Suspension)

Layout


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6.3.2

Textbook

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ECAS is made up of the following three components.
▪ Buffering unit: Air spring, variable damper (vehicle height/damper damping force adjustment)
▪ Pneumatic unit: Air injection valve, air filter, compressor, valve block, air tube, reservoir tank
(air-supply/discharge)
▪ Control unit: Vehicle height sensor, G sensor, pressure sensor, ECS mode switch, ECS ECU, ECS

lamp (sensor signal processing and vehicle position control)
The pneumatic circuit of the pneumatic unit and buffering unit is a closed one and promotes air-flow for
vehicle height control.

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6.3.3

Module6 ECS (Electronic Control Suspension)

Components

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1) Absorption Section

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1 Air Spring

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Front-wheel air springs are attached to variable dampers. Rear-wheel air springs are detached from
dampers, allowing air to be filled or discharged through the air tube for vehicle height adjustment. Other
components include a urethane pad for spring unit impact absorbance and a protector for keeping out
contaminants.
2 Variable Damper

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ECS ECU monitors vehicle movement and adjusts damper damping force to suit the driving conditions.
It maintains an optimum vehicle position for given driving conditions for ride comfort, enhanced control
and individual-wheel control.

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Control current volume is 0A-1.6A; when high currents are recognized, the plunger moves to the right
to expand the orifice through which oil passes (soft mode). Conversely, recognition of low currents
moves the plunger to the left to constrict the orifice (hard mode).

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2) Air Pressure Section
1 Air Filling Valve
A valve for injecting air into air springs. Connected to the reservoir tank, the air injection valve injects
air through diagnostic equipment.
2 Air Tube
An air tube is a pneumatic component (e.g. air spring, valve block, etc) through which air travels.
Ensure that the colored marking at the end of the tube remains on for tube distinction in assembly.

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3 Reservoir Tank

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A reservoir tank is located at the front left of a vehicle and supplies pressure to the compressor for
vehicle elevation and stores air released from air springs during vehicle descension. Reservoir rank
capacity is 5.2L.

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4 Compressor


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A compressor distributes air in the reservoir tank to air springs or sends back air to the reservoir tank
from air springs. It functions when there is an air shortage in the system.

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A compressor is made up of a motor, two reserving valves (2EA), relief pressure valve, check valve
and dryer. There are three air ports, each of which connects to the valve block, reservoir tank and air
exchange hose.

• Reversing Valve
Installed inside the compressor, a reversing valve converts the flow of the internal valve for air spring
air supply/discharge.

• Relief Pressure Valve
Installed on the compressor, a relief pressure valve is a safety device that discharges air when the
compressor's internal pressure reaches a hazardous level.
• Air Dryer
Absorbs moisture in the air to keep the system moisture-free. Humidity is discharged along with air.

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Module6 ECS (Electronic Control Suspension)

5 Valve Block
A valve block is located behind the right fog lamp. Made up of five solenoid valves and air ports, a
valve block distributes air to air springs and the reservoir tank. There is an internal pressure sensor.
Solenoid valves open and close ports for pneumatic pressure transfer according to electric signals.
Being an N/C-type device, solenoid valves remain closed by air spring pressure until opened by ECU
for air transfer. Using a pressure sensor, a valve block monitors the internal pressure in the air tank
and springs.

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The air ports are made up of a reversing valve, which returns air to the four air springs and compressor,
and a port leading to the air filter.
6 Air Filter

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3) Control Section

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Located on the top left of the wheel house to the right of the engine room, the air filter filters the air
sucked into the system.

1 Vehicle Height Sensor

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Four vehicle height sensors are installed on the vehicle body and lower arm to detect the acceleration
of the top/bottom of the vehicle body. The hall IC detects vehicle height change from sensor movement
and sends signals to ECS ECU. In vehicle height control, the vehicle height sensor is used for vehicle
height measurement; in damping force control, it is used for estimating the relative speed of each
corner damper.

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2 G Sensor

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An acceleration sensor is installed on FL, FR and RL for measuring the vehicle body's vertical
acceleration and sending signals to ECS ECU. Based on incoming vehicle body vertical acceleration
signals, ECU calculates the vehicle's top/bottom, pitch, roll and vibration speed. Based on these
speed elements, damping force is controlled to suppress vehicle body vibration.

3 Pressure Sensor

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Installed on the valve block, a pressure sensor detects pressure in the system. When ECS is not
operating, it monitors system pressure for the reservoir tank; when ECS is operating, it monitors system
circuit pressure for air spring operation.

4 ECS Mode Switch


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Four vehicle height sensors are installed on the vehicle body and lower arm to detect the height of the
vehicle when moving. The vehicle body's top/bottom acceleration is sent to ECS ECU as signals from
the sensor rod for use in vehicle height control.

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• Vehicle Height Control Switch

The driver can change the vehicle height by selecting high mode or normal mode. Low mode is not
switch-selectable and is enabled automatically when the vehicle maintains a speed of 120km/h or
higher for more than 10 seconds.
• Damping Force Control Switch
The driver can adjust damping force by selecting sport mode or auto mode.

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Module6 ECS (Electronic Control Suspension)

5 ESC ECU
ESC ECU is located in the LH trim in the trunk and receives driving conditions/position signals from
sensors and controls the vehicle height and damping force. Vehicle height is controlled automatically
according to vehicle speed; it can be controlled using the vehicle height control button also.

6 ECS Lamp

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The ECS indicator is located on the cluster. The "High" lamp is switched on when high mode is enabled
for vehicle height control. The "Sport" lamp is switched on when sport mode is enabled for damping
force control.

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6.3.4

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Control

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1) Input & Output Elements

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ECS ECU detects vehicle movement through the vehicle height sensor, G sensor and pressure sensor,
and recognizes the driver's intentions through the ECS mode switch. Calculations for vehicle height and
damping force control are made based on data received from ECM, ABS/ESC and MDPS. Air flow is
controlled through the solenoid valve, exhaust valve, reversing valve and compressor relay to increase or

decrease vehicle height. Damping force is made hard or soft through the variable damper valve for ride
comfort and driving stability.

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2) Vehicle Level Control
Overview

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Vehicle height can be controlled while driving or stationary manually or automatically.
The driver the can manually control the vehicle height switch to select one of two levels (normal/off-road).
Auto mode lets ECU adjust vehicle height to level ideal for given driving conditions. Adjustable levels
include Normal (design height), Highway (low) and Off-road (high).
Pneumatic control occurs as shown in the diagram below for height height control when certain
conditions are met.

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Vehicle control is based on vehicle height sensor signals (4EA), pressure sensor signals, wake-up
signals (vehicle IGN signals) and CAN signals.

Level Operating Modes

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Reservoir pressure is checked after a set time when vehicle height control is finished. In case of a
pneumatic pressure shortage, a refill takes place only when traveling at a certain speed for the following
control. The reason a certain speed is required is because noise and vibration are likely to occur from
compressor activation.

Vehicle control takes place in the various operating modes of ECU.

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• Sleep state


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Sleep mode reduces ECU's power consumption. Level control is disabled in sleep mode. Sleep mode
is exited when ECU detects a ECU wake-up pin or when IGN is switched on. After IGN switch-off,
ECU enters sleep mode after a set delay time. A vehicle left in sleep mode for a prolonged time wakes
up ECU every two, five and ten hours (adjustable) for normal vehicle height maintenance.
• Wakening state

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The period between IGN switch-off and sleep mode entry is referred to as wakening mode. In this
mode, vehicle height cannot be manually controlled using HMI and only automatic vehicle height
control takes place.

• IGNITION state
ECU enters ignition mode if the IGN switched on but the engine fails to start. Level control is not
available in this mode.

• Standstill state
ECU converts to standstill mode if the IGN switched on and the engine starts. Level change the user
desires can take place in this mode.
• Drive state
ECU enters drive mode when a certain speed threshold (adjustable) is reached. In this mode, both
manual and automatic level change can take place. Manual level change requires the vehicle speed
to be under 70; if higher than 70, vehicle height is returned to normal automatically. Vehicle height
is automatically lowered when vehicle speed of 120 or higher is maintained for 10 seconds, before
returning to normal when vehicle speed is maintained at 80 or lower for 5 seconds.

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• CarLift state

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When a vehicle is placed on a lift for maintenance, the space between its wheels and body widens.
The vehicle recognizes this as increased vehicle height and the automatic vehicle height calibration
function can lower the vehicle body, resulting in air discharge from air springs. To prevent this issue,
put the vehicle in the "car lift state" to prevent unnecessary vehicle height control. Car list mode is
changed to ignition mode if ignition is turned on, and changes to drive mode if vehicle speed increases.

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3) Damping Control
Overview

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The body of a moving vehicle vibrates constantly due to contact with (uneven) road surfaces, possibly
causing the driver discomfort. Damping control prevents this issue through continuous damping force
control through variable dampers for optimum ride comfort and driving stability.
Skyhook

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Skyhook control is one of the most effective algorithms for vehicle suspension damping control. From
virtual coordinates located in the space above a vehicle, the vehicle body's up/down vibration is detected
and skyhook dampers' damping force is increased appropriately to reduce vehicle body vibration.

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Ride comfort control
• Anti-squat: Changes all CDC dampers from soft to hard during sudden acceleration, before gradually
reverting to soft mode (check engine torque)
• Anti-Dive: Changes all CDC Dampers from Soft→Hard during sudden braking, and slowly restores
Soft Mode (check brake pressure)
• Anti-Roll: Changes all CDC Dampers from Soft→Hard during hard turn, and slowly restores Soft

Mode (check Latitudinal-G and steering angle)

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Module6 ECS (Electronic Control Suspension)

• Anti-Dive: Changes all CDC Dampers from Soft→Hard during sudden braking, and slowly restores
Soft Mode (check brake
• Bump mode: Changes all CDC Dampers from Soft→Hardwhen a bump is driven over, before

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gradually reverting to soft mode (check vehicle height)

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4) Air Supply System Control

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A pneumatic circuit is made up of a compressor, valve block, reservoir tank and four air springs. Air
flow in the pneumatic circuit is controlled for vehicle height control, air spring air discharge and pressure
measurement/control.


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An open-loop system was used in the past, which produced limited energy efficiency from slow vehicle
height control resulting from external air exchange during forced exhaust. On the other hand, the latest
closed-loop systems achieve fast vehicle height control and high energy efficiency.

1. Compressor

8. Air Spring Valve

2. Air Dryer

9. Pressure Sensor

3. Throttle / Check Valve

10. Relief Pressure Valve

4 / 5. Reversing Valves


11. Air Filling Valve

6. Reservoir Tank

12. Suction Hose with Air Filter

7. Environment Valve

13. Exhaust Hose

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Decrease Ground Clearance

When vehicle height is increased, the motor in
the compressor starts up to supply air in the
reservoir to the valve block through the reversing
valve. Solenoid valves in the valve block then
supply air to the air springs to lift the vehicle
body up.

Air supplied to the air springs from the reservoir
tank are returned to the reservoir tank through

the air dryer, resulting in increased reservoir tank
pressure.

Air Refill

Air Exhaust

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Increase Ground Clearance

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When the system is short of air, external air
is sucked in through the external air filter for
pressure supplementation.

Excess pressure in the system is removed by
releasing air into the atmosphere through the

external air filter.

Air is released into the atmosphere through the
reversing valve, environment valve and air filter.

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Air-Filling

Air is filled through the air injection valve when
more air is required in the ECS system.
Air sucked in through the reservoir tank is
supplied to the four air springs by the compressor
motor.

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Module6 ECS (Electronic Control Suspension)

6.4

Maintenance (for ECAS)


6.4.1

Cautionary Measures for Handling
Different Parts

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1) FW Air Strut
▪ To assemble the FW strut, assemble the lower part first and raise the lower arm before assembling the
upper part (potential buckling if done in the reverse order)
▪ Do not hold the gaiter or cable when loading or moving the FW strut (potential bellows damage from
exterior defect/interior interference or CDC malfunction from cable disconnection)

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Do not hold when loading/moving.

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▪ Check for air inside the springs and any distortion (potential damage from a distorted bellows)

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2) Rear Air Spring

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CAUTION

▪ Do not pull on rear air springs during maintenance
▪ Check the state of the upper pad and bearing installation when assembling rear air springs

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▪ Do not lower the vehicle onto the floor and fill air after changing air springs (air spring buckling highly
likely)
→ Fill air with the vehicle lifted up, i.e. with all wheels fully rebound

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→ Replace springs with new ones if buckling occurs

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