Mitsubishi Outlander (2013+). Manual - part 61

CONSTRUCTION DESCRIPTION

ANTI-SKID BRAKING SYSTEM (ABS)

35B-8

NOTE: 

.

•

*

: The ABS warning lamp and the brake warning lamp stay on until the ignition switch is turned to the 

LOCK (OFF) position.

•

When the brake fluid level in the brake fluid reservoir tank is lower than the specified value, or when the 
parking brake lever is pulled, the brake warning lamp turns ON.

ABS-ECU

M2351003001028

• 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 <4WD>, no sensor 

harness is required, enhancing the reliability.

• Self-diagnostic and memory functions are inte-

grated into ABS-ECU. If any malfunction is 
detected by the self-diagnostic function, 
ABS-ECU activates a fail-safe function and illumi-
nates the ABS warning lamp and brake warning 

lamp

*

.

NOTE: *: The brake warning lamp is used as the 

EBD control warning lamp.

• ABS-ECU detects vehicle speed from the signals 

of the wheel speed sensor and its incorporated G 
sensor <4WD>, recognizes the wheel rotation 
status, estimates the wheel slip condition based 
on the preprogrammed algorithm, and then con-
trols the solenoid valve in the hydraulic unit so 
that the wheels do not lock.

CONSTRUCTION DESCRIPTION

ANTI-SKID BRAKING SYSTEM (ABS)

35B-9

ABS fluid pressure control

ABS control cycle

1. The ABS-ECU calculates the speed and deceler-

ation of each wheel based on the signals from the 
four wheel speed sensors and the G sensor 
<4WD> incorporated in the ABS-ECU, and esti-
mates 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 sig-
nal 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).

AC506830AB

a

b

c

d

A

B

C

D

e

Increase
Hold
Decrease

Wheel speed

Brake pressure

Actual vehicle speed

Estimated vehicle speed

CONSTRUCTION DESCRIPTION

ANTI-SKID BRAKING SYSTEM (ABS)

35B-10

EBD fluid pressure control

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 cer-

tain 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 lamp for 3 seconds (including the initial 

check) 

*

 after the ignition switch is turned ON. If any 

malfunction is detected, ABS-ECU continues illumi-
nating the ABS warning lamp and disables ABS con-
trol.

NOTE: 

*

: The ABS warning lamp may stay on after 

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

STARTUP CHECK

When the startup vehicle speed reaches approxi-
mately 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 <4WD>.

(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 <4WD>.

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.

AC208548AB

Ideal distribution curve when 
seated by fixed persons

EBD operating conceptual design

Rear braking force

Ideal distribution curve when seated by one persons

Braking force distribution curve 
by the existing proportioning valve

Braking force distribution 
by EBD control

Front braking force

Braking Force 
Improved

CONSTRUCTION DESCRIPTION

ANTI-SKID BRAKING SYSTEM (ABS)

35B-11

(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.

FAIL-SAFE FUNCTION

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

lamp and brake warning lamp

*

, and it disables ABS 

and EBD control.

NOTE: *: The brake warning lamp is used as EBD 
control warning lamp.

DIAGNOSTIC FUNCTION

ABS-ECU has the following functions for easier sys-
tem checks. The following items can be diagnosed 
using M.U.T.-III.

• Diagnosis code set

• Service data output

• Actuator test

• Freeze frame data output