6.6 ABS / TCS / EBD / ESP

6.6.1 Specifications
6.6.1.1 Fastener Tightening Specifications

Applications

Model

Specifications

Metric (Nm)

US English (lb-ft)

Wheel Speed Sensor Harness
Connector Bolts

M6 × 18

19-22

14-16.3

ABS Bracket Strengthening
Plate Assembly Nut

M8

23-30

17-22.2

6.6.1.2  Wheel  Speed  Sensor  Technical
Specifications

Wheel Speed Sensor

Description

Sensor Type

Hall-type Speed Sensor

Voltage

4.5-20 V

Signal Current

Low: 7 ± 20% mA, High: 14 ± 20% mA

Gap Between The Signal Plate and The Sensor

Front Axle 1.56 mm (0.06 in) Rear Axle 0.738 mm (0.03 in)

Brake System

ABS / TCS / EBD / ESP

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6.6.2 Description and Operation
6.6.2.1 Description and Operation

This vehicle is equipped with anti-lock braking system (ABS)
and  electronic  brake-force  distribution  (EBD)  system.  In
addition  to  in  the  original  brake  system,  the  following
components are added:

Hydraulic Electronic Control Unit (HECU):

Note

Between  hydraulic  electronic  control  unit  installation
bolts and bracket, there are rubber anti-vibration pads,
which are used to avoid the hydraulic electronic control
unit being affected by the vehicle vibration. The hydraulic
electronic  control  unit  can  not  be  disassembled,  and
must be replaced as an assembly.

The hydraulic electronic control unit (HECU) controls system
function and detect faults. When the ignition switch is turned
on and there are no anti-lock braking system DTC codes, the
system  provides  power  to  the  relay,  so  the  battery  positive
voltage is provided to the solenoid valve and pump. Hydraulic
electronic control unit (HECU) continuously tests the wheels
status to control wheel slip rate within a certain range so as to
maintain  the  vehicle  stability.  Hydraulic  control  piping  uses
diagonal configuration, so that from the brake master cylinder
one channel fluid flows along the left front to right rear wheel,
the other flows from the right front to the left rear wheel. Two
channels are isolated, so that when one brake channel fails or
leaks, the other will make sure the continuous braking ability.
Hydraulic electronic control unit (HECU) includes the following
main components:

–

ABS control module

–

ABS Pump and Relay

–

Inlet Valve, each valve controls one wheel

–

Outlet Valve, each valve controls one wheel

–

Electromagnetic Coil Relay

Wheel Speed Sensor:

Wheel  speed  sensor  is  a  Hall-type  speed  sensor.  With  the
wheels  rotating,  ABS  control  module  uses  the  wheel  speed
signal to calculate the wheel speed. Wheel speed sensor can
be individually replaced, but the signal plate (Gear) is fitted on
the axle and must be replaced together with the axle.

Brake Lamp Switch:

Press the brake pedal, the brake lamps are lit, while signals are
sent to the ABS brake control module.

ABS Warning Lamp:

Located on the instrument cluster, light to notify the driver the
ABS failure when the following events occurs:

–

ABS control module detects the ABS system malfunction,
the  instrument  cluster  receives  a  request  for  lighting  the
ABS  warning  lamp  through  the  CAN  bus  from  the  ABS
control module.

–

Instrument  cluster  carry  out  self-test  in  the  beginning  of
each ignition cycle, the indicator light about 3s.

–

Instrument cluster detects the communication to the ABS
control module is lost.

EBD Warning Lamp:

Located on the instrument cluster, light to notify the driver EBD
failure. When the ABS Warning Lamp is lit, but EBD warning
lamp is not lit, the system will still have EBD function. When the
ABS Warning Lamp and EBD warning lamp are all lit, ABS and
EBD function all fail.

Self-diagnostic Test:

ABS control module performs a self-diagnostic test each time
the  ignition  switch  is  turned  to  on.  As  long  as  the  ABS  is
provided  power  and  in  a  working  status,  it  monitors  the
performance. Once a fault is detected, it will trigger an alarm
until  the  fault  disappears.  ABS  error  code  will  be  stored  in
memory until being manually erased.

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ABS / TCS / EBD / ESP

Brake System

6.6.3 System Working Principle
6.6.3.1 System Working Principle

Anti-lock Braking System (ABS) Hydraulic Piping Diagram

AV

EV

FL

RR

RL

FR

AV

M

LPA

EV

AV

EV

AV

EV

FE06-5601b

Orifice

Legend

1. AV-Inlet Solenoid Valve
2. EV-Outlet Solenoid Valve
3. LPA-Low Pressure Accumulator
4. M-Motor
5. FL-Left Front Wheel

6. RR-Right Rear Wheel
7. RL-Left Rear Wheel
8. FR-Right Front Wheel

Anti-lock Braking System (ABS)

In  the  anti-lock  braking  period,  anti-lock  braking  system
controls  each  wheel  braking  fluid  pressure  to  prevent  wheel
slip.  Each  wheel  is  equipped  with  a  separate  and  specific
hydraulic fluid line solenoid valve. Anti-lock braking system can
reduce,  maintain  or  increase  brake  fluid  pressure  to  each
wheel. However, the anti-lock braking system can not make the
pressure exceed the pressure provided by the brake master
cylinder. During the anti-lock braking, a series of rapid pulse
can be felt on the brake pedal. When the ABS control module

detects the speed sensor input and tries to prevent wheel slip,
each solenoid valve position rapidly changes. ABS pump starts
working, resulting pulse. Pedal pulse only appears during the
anti-lock braking, and disappears during the normal braking or
parking. For vehicles equipped with anti-lock braking system,
apply normal force on the brake pedal can stop the vehicle.
Anti-lock  braking  system  can  effectively  shorten  the  braking
distance and maintain the vehicle stability. During the anti-lock
braking, brake system pressure is adjusted in three stages.

Brake System

ABS / TCS / EBD / ESP

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Pressure Maintaining

When  the  wheel  spins,  ABS  control  module  closes  the  inlet
valve and keeps the valve closed and isolated from the system.
It  maintains  the  braking  fluid  pressure  without  increasing  or
decreasing.

Pressure Decrease

When  the  wheel  spins,  ABS  control  module  reduces  the
pressure  to  individual  wheels  during  deceleration.  The  inlet
valve is closed, while the outlet valve is open. The excess fluid
is stored in the accumulator until the ABS pump returns the fluid
to the master cylinder.

Pressure Increase

When the wheel does not spin, ABS control module gradually
increases the braking pressure to each wheel to reduce wheel
speed. The inlet valve is open, while the outlet valve is closed.
The  increased  pressure  is  provided  by  the  brake  master
cylinder.

Electronic Brake Force Distribution (EBD)

Each wheel attached ground conditions may be different, then
the ground friction coefficient will be different. During braking,
the vehicle gravity center will change, so the vehicle is prone
to skid when braking, tilt and roll and so forth. EBD's function
is to calculate four tires friction difference as a result of different
adhesion coefficients at the braking moment, then adjust the
hydraulic unit electromagnetic valve. The valve adjusts as the
preset  program  to  match  the  system  power  to  the  friction
(adhesion), ensure vehicle braking smooth and safety. Under
the emergency braking situation, before the ABS action EBD
has  balanced  each  wheel  grip,  to  prevent  tail-flick  and  the
lateral movement. EBD is actually an additional ABS function.
Based on road and load changes, it automatically adjusts the
braking force distribution, improves and the ABS efficiency.

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ABS / TCS / EBD / ESP

Brake System