Mitsubishi Galant (2004+). Manual — part 1697

CONSTRUCTION DESCRIPTION

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

35B-9

SERVICE DATA OUTPUT
The data input from all sensors and switches can be
read using the scan tool.

.

ACTUATOR TESTING
The scan tool can be used to force-drive all solenoid
valves and the pump motor.

MUT-III SCAN TOOL DISPLAY

ITEM NO.

CHECK ITEM

DISPLAY OR UNIT

FR wheel speed sensor

01

Front-right wheel speed sensor

km/h or mph

FL wheel speed sensor

02

Front-left wheel speed sensor

km/h or mph

RR wheel speed sensor

03

Rear-right wheel speed sensor

km/h or mph

RL wheel speed sensor

04

Rear-left wheel speed sensor

km/h or mph

Battery voltage

05

ABS-ECU power supply voltage

V

Stoplight switch

06

Stoplight switch

ON/OFF

MUT-III SCAN TOOL
DISPLAY

ITEM NO.

ITEM

PARTS TO BE ACTIVATED

FR Wheel ABS Drive

01

Solenoid valve for front-right wheel

Solenoid valves and pump
motors in the hydraulic unit
(simple inspection mode)

FL Wheel ABS Drive

02

Solenoid valve for front-left wheel

RR Wheel ABS Drive

03

Solenoid valve for rear-right wheel

RL Wheel ABS Drive

04

Solenoid valve for rear-left wheel

SYSTEM OPERATION

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

35B-10

SYSTEM OPERATION

M2351004000170

ORDINARY BRAKING MODE (ABS IS
OPERATIVE)

In an ordinary braking mode, no current is supplied
from the ABS-ECU to the solenoid valves IN and
OUT. Therefore, the valves IN are kept in the opened
position, while the valves OUT are kept in the closed
position.

When the brake pedal is depressed, the fluid in the
master cylinder flows through solenoid valve IN to
the wheel cylinders and the brakes are applied.
When the brake pedal is released, the fluid pressure
in the master cylinder decreases, and the fluid
returns through solenoid valve IN and check valve to
the master cylinder to release the brakes.

SOLENOID VALVE

CURRENT SUPPLY

VALVE POSITION

PASSAGE OPENED/CLOSED

IN

OFF

Opened

Master cylinder to wheel cylinder

OUT

OFF

Closed

Wheel cylinder to reservoir

AC308606 AB

CHECK VALVE

WHEEL CYLINDER

SOLENOID
VALVE IN

SOLENOID
VALVE OUT

RESERVOIR

PUMP AND
MOTOR UNIT

MASTER CYLINDER

BRAKE DURING PEDAL DEPRESSED

BRAKE DURING PEDAL RELEASED

SYSTEM OPERATION

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

35B-11

ABRUPT BRAKING (ABS OPERATING)

.

PRESSURE REDUCING MODE
When the wheels are about to be locked due to
abrupt brake application for example, the ABS-ECU
outputs a "reduce the pressure" signal to the sole-
noid valves and causes the valves to be energized.
As a result, the solenoid valves IN close, blocking the
fluid passage from the master cylinder. The solenoid
valves OUT, on the other hand, open, clearing the
fluid passage from the wheel cylinders to the reser-
voir.

As a result, the fluid pressure in the wheel cylinders
decrease as the fluid flows through solenoid valve
OUT back to the reservoir.

.

SOLENOID VALVE

CURRENT SUPPLY

VALVE POSITION

PASSAGE OPENED/CLOSED

IN

ON

Closed

Master cylinder to wheel cylinder

OUT

ON

Opened

Wheel cylinder to reservoir

AC308612

WHEEL CYLINDER

SOLENOID
VALVE IN

SOLENOID
VALVE OUT

RESERVOIR

PUMP AND
MOTOR UNIT

MASTER CYLINDER

AB

SYSTEM OPERATION

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

35B-12

PRESSURE HOLDING MODE
When the fluid pressure in the wheel cylinder is
reduced to an optimum level, the ABS-ECU outputs
a "hold the pressure" signal to the solenoid valves,
causing the solenoid valves IN to be energized,
whereas the solenoid valves OUT to be de-ener-
gized.

As a result, all the solenoid valves IN and OUT are
closed, blocking the fluid passages in order to retain
the fluid pressure in the wheel cylinders.

.

SOLENOID VALVE

CURRENT SUPPLY

VALVE POSITION

PASSAGE OPENED/CLOSED

IN

ON

Closed

Master cylinder to wheel cylinder

OUT

OFF

Closed

Wheel cylinder to reservoir

AC308622

WHEEL CYLINDER

SOLENOID
VALVE IN

SOLENOID
VALVE OUT

RESERVOIR

PUMP AND
MOTOR UNIT

MASTER CYLINDER

AC