Mitsubishi Outlander XL. Manual - part 1285

CONSTRUCTION DESCRIPTION

SENSOR

M23501000010USA0000010000

WHEEL SPEED SENSOR

ZC6006670000

Front

Rear

Front wheel speed sensor

Rear wheel speed sensor

Encoder for 
wheel speed detection

Encoder for 
wheel speed detection

The wheel speed sensor is a kind of a pulse generator.
It consists of the magnetic encoder for wheel speed
detection (a plate on which north and south pole sides
of the magnets are arranged alternately) which rotates
at the same speed of the wheel and the wheel speed
sensor (semiconductor sensor). This sensor outputs
frequency  pulse  signals  in  proportion  to  the  wheel
speed.

The  front  wheel  speed  sensor  consists  of  the  front
wheel speed sensor mounted on the knuckle and the
magnetic encoder for wheel speed detection which is
press-fitted together with the oil seal to the front wheel
bearing. The rear wheel speed sensor consists of the
rear wheel speed sensor mounted on the trailing arm
assembly and the magnetic encoder for wheel speed
detection,  which  is  press-fitted  together  with  the  oil
seal to the rear wheel bearing.

G SENSOR <AWD>

The  G-sensor  is  incorporated  in  ABS-ECU,  and
detects longitudinal acceleration of a vehicle.

Actuator

M23501000020USA0000010000

ABS warning light, Brake warning light

The ABS system informs the driver to the ABS system
status  by  illuminating,  extinguishing,  or  flashing  the
ABS warning light and brake warning light as follows.

ABS warning light

｠

Turns ON when the system malfunction occurs.

Brake warning light

｠

Turns  ON  when  the  EBD  system  malfunction
occurs.

NOTE:

｠

Turns  ON  when  the  brake  fluid  level  in  the
reservoir  tank  becomes  the  specified  value  or
lower than that.

｠

Turns ON when the parking brake lever is pulled
and the brake is activated.

ABS warning light and brake warning light illumination or flashing pattern

State

ABS warning light

Brake warning light

Normal

Correct

-

-

35B-6

FOUR-WHEEL ANTI-LOCK BRAKE SYSTEM (4ABS)

CONSTRUCTION DESCRIPTION

State

ABS warning light

Brake warning light

Faulty

ABS failure

Illuminates

-

EBD failure

Illuminates

Illuminates

When  scan  tool  is
connected

Actuator not operated

-

-

Actuator operated

Flash (2Hz)

-

ABS-ECU

M23501000030USA0000010001

｠

By integrating ABS-ECU into the hydraulic unit, no
wiring  harness  for  sending  drive  signal  of  the
solenoid  valve  and  pump  motor  is  required,
assuring higher reliability.

｠

By incorporating the G-sensor, no sensor harness
is required, enhancing the reliability. <AWD>

｠

Self-diagnostic  and  memory  functions  are
integrated  into  ABS-ECU.  If  any  malfunction  is
detected by the self-diagnostic function, ABS-ECU

activates  a  fail-safe  function  and  illuminates  the
ABS warning light and brake warning light*.

NOTE: 

*: The brake warning light is used as the

EBD control warning light.

｠

ABS-ECU detects vehicle speed from the signals of
the  wheel  speed  sensor  and  its  incorporated  G
sensor  <AWD>,  recognizes  the  wheel  rotation
status, estimates the wheel slip condition based on
the  preprogrammed  algorithm,  and  then  controls
the solenoid valve in the hydraulic unit so that the
wheels do not lock.

ABS hydraulic pressure control

ABS control cycle

ZC500796

a

b

c

d

A

B

C

D

Estimated vehicle speed

Actual wheel speed

Pressure increase

Hold

Pressure decrease

Wheel speed

Brake pressure

e

FOUR-WHEEL ANTI-LOCK BRAKE SYSTEM (4ABS)

35B-7

CONSTRUCTION DESCRIPTION

1.

The  ABS-ECU  calculates  the  speed  and
deceleration of each wheel based on the signals
from  the  four  wheel  speed  sensors  and  the  G
sensor  incorporated  in  the  ABS-ECU,  and
estimates the vehicle speed at that time.

2.

When the brake pedal is depressed, the brake fluid
pressure applied to the wheel cylinder increases,
and  the  wheel  speed  decreases.  When  the
difference between the wheel speed and vehicle
speed  increases,  and  the  vehicle  deceleration
goes  below  the  specified  value  (Point  A),  ECU
determines that the wheels are about to be locked.
At this time, ECU reduces the brake fluid pressure
by outputting the pressure decrease signal to the
solenoid valves (IN, OUT). (between a and b)

3.

When the vehicle deceleration and wheel speed
begin recovery, and the vehicle speed reaches the
point B, ECU outputs the pressure hold signal to
maintain  the  wheel  cylinder  fluid  pressure.
(between b and c)

4.

When  the  wheel  speed  deceleration  is  further
recovered  and  overpasses  the  point  C,  ECU
determines that the wheel lock possibility has been
eliminated and increases the brake fluid pressure
by outputting the pressure increase signal again.
(between c and d)

5.

Brake fluid pressure is controlled by repeating the
increase and hold of the pressure. (between d and
e)

6.

When  the  wheel  deceleration  goes  below  the
threshold again, ABS-ECU controls the brake fluid
pressure by repeating the cycle (Step 2 to 5).

Four-wheel control
ABS fluid pressure is controlled independently for four
wheels.

EBD hydraulic pressure control

ZC500798

Ideal distribution curve for  
fixed passengers boarding

Brake force distribution curve by  
conventional proportioning valve

EBD operation conceptual diagram

Rear braking force

Front braking force

Ideal distribution curve for  
one passenger boarding

Enhanced braking force

EBD braking force distribution range

EBD control is activated in a range with lower slip ratio
where  ABS  is  disabled.  EBD  calculates  vehicle
deceleration and slip amount of the four wheels based
on the wheel speed sensor signal. If the rear wheel
speed differs from the vehicle speed by a certain level
or  more,  EBD  increases,  holds,  and  decreases  the
pressure at the rear wheel control solenoid valve in
the hydraulic unit, and then adjusts rear wheel brake
fluid pressure fairly close to an ideal distribution curve.

INITIAL CHECK

ABS-ECU performs the following initial checks using
the  diagnostic  functions.  ABS-ECU  illuminates  the
ABS warning light for 3 seconds (including the initial
check)*after  the  ignition  switch  is  turned  ON.  If  any
malfunction  is  detected,  ABS-ECU  continues
illuminating the ABS warning light and disables ABS
control.

NOTE: 

 *: The ABS warning light may stay on after

the ignition switch is turned ON until the startup

35B-8

FOUR-WHEEL ANTI-LOCK BRAKE SYSTEM (4ABS)

CONSTRUCTION DESCRIPTION

vehicle speed reaches approximately 10 km/h. As
far as ABS-ECU memorizes any diagnostic trouble
code related to the wheel speed sensor malfunction
recorded during the previous ignition ON status,
ABS-ECU continues illuminating the ABS warning
light until it verifies that the malfunction for
that code is resolved (startup check).

INITIAL CHECK
Performs self-diagnosis in ABS-ECU.

STARTUP CHECK

When  the  startup  vehicle  speed  reaches
approximately  10  km/h,  ABS-ECU  performs  the
following checks.

1.

Motor, solenoid valve check (Initial startup*only)
Turns ON the motor relay in ECU, and checks the
pump motor operation. At the same time, ABS-ECU
sequentially energizes each solenoid valve in a very
short period and checks the valve operation.

NOTE: 

 *: Initial startup indicates a first

startup after the system has started.

2.

Wheel speed sensor check
ABS-ECU  checks  for  any  wheels  that  have  not
received  wheel  speed  sensor  signal  from  the
startup.

CONSTANT CHECK

ABS-ECU constantly checks the following items.

1.

ABS-ECU

(1)

Performs self-diagnosis in ECU.

(2)

Checks for abnormal output voltage of G sensor,
and detects open or short circuit in the G sensor.
<AWD>

(3)

Checks  the  output  voltage  for  G  sensor,  and
determines that the G sensor is stuck when the
output  voltage  exceeding  the  specification
continues for a certain period or more. <AWD>

2.

ECU power supply
Checks if ECU power supply voltage stays within
the operational range.

3.

Wheel speed sensor

(1)

Monitors the output voltage of the sensor signal
wiring harness and checks for abnormal output
voltage (open/short circuit).

(2)

Checks for any wheels that do not send pulse
signal while the vehicle is in motion.

(3)

Checks  if  wheel  speed  which  is  abnormally
higher or lower than the vehicle speed is input.

4.

Pump motor, solenoid valve
Checks  that  the  ABS-ECU  output  signal  and  the
operating  conditions  of  the  pump  motor  and
solenoid valve agree with each other.

CAN COMMUNICATION

ABS-ECU outputs the ABS warning light and the EBD
warning  light*illumination  request  signals  to  the
combination meter through CAN communication.

NOTE: 

*: The brake warning light is used as EBD

control warning light.

FAIL-SAFE FUNCTION

If any malfunction is detected by the self-diagnostic
function, ABS-ECU illuminates the ABS warning light

and  brake  warning  light*,  and  it  disables  ABS  and
EBD control.

NOTE: 

*: The brake warning light is used as EBD

control warning light.

DTC
code
No.

Item

Countermeasures for failure
EBD control

ABS control

Brake
warning light

ABS  warning
light

C100A Abnormality in FL wheel speed

sensor circuit

Executed
(Prohibited
when  two  or
more  wheels
are faulty.)

Prohibited

Extinguished *
2

Illuminated*3

C1015 Abnormality in FR wheel speed

sensor circuit

C1020 Abnormality in RL wheel speed

sensor circuit

C102B Abnormality in RR wheel speed

sensor circuit

FOUR-WHEEL ANTI-LOCK BRAKE SYSTEM (4ABS)

35B-9

CONSTRUCTION DESCRIPTION