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