E Textbook Power Train & Chassis M2

1. SUPER SELECT 4WD SYSTEM
(7) Shift Rails
The main shift rail, 2WD/4WD shift rail and high/low shift rail are moved by a selected drive system. A
switch to detect the current drive system is mounted on each shift rail.
- When 2H is selected -
When 2H is selected, the main shift rail moves to the right side and the 2WD/4WD shift rail and high/
low shift rail move to the left side as shown below. The 2WD detection switch and 2WD/4WD detec-
tion switch turn ON with the groove provided on each shift rail to detect that the 2WD state is current-
ly applied.

2WD operation detection switch

Fig. 1-32

- When 4H is selected -
When 4H is selected, the main shift rail moves to the left side from 2H, and the 2WD/4WD shift rail
moved to the right side by intermediate gear. At this time, the 2WD/4WD detection switch and 4H de-
tection switch turn ON to detect that the full-time 4WD state is currently applied.

Fig. 1-33

1 - 17 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

- When 4HLc is selected -

At 4HLc is selected, the main shift rail moves to the left side from 4H, and the 2WD/4WD shift rail is
moved to the right side by the intermediate gear. This intermediate gear is missing some teeth, so
even if the main shift rail attempts to move further to the right, rotation is prevented. At this time, the
4H detection switch and centre differential lock detection switch turn ON to detect that the direct cou-
pled 4WD (high range) state is currently applied.

Fig. 1-34

- When 4LLc is selected -

When 4LLc selected, the main shift rail moves to the left side from 4HLc, and the high/low shift rail is
moved to the right by the intermediate gear. At this time, the centre differential lock detection switch
and 4LLc detection switch turn ON to detect that the direct coupled 4WD (low range) state is current-
ly applied.

MMMTC VER 1 MAC17 Fig. 1-35
1 - 18

1. SUPER SELECT 4WD SYSTEM

3. Freewheel Mechanism
A vacuum type freewheel clutch has been adopted, and it has the following features.
◇ This device is composed of main shaft, clutch sleeve, clutch gear, shift rod, and shift fork, etc.
◇ The freewheel clutch assembly is electrically and automatically controlled utilizing an ON/OFF

signal from the 2WD/4WD detection switch which is located in the transfer.
◇ The solenoid valves are either activated or deactivated to change the passage of vacuum to the

actuator according to the ON/OFF signal. Operated by the actuator, via the shift rod and shift
fork, the clutch sleeve slides to either 2WD or 4WD position to select the drive train mode.
◇ A vacuum tank is incorporated to provide a better freewheel clutch operation.

<Construction Diagram>

2WD/4WD detection
switch

Fig. 1-36

1 - 19 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

<Freewheel Clutch Operation>

◇ 2WD
When the transfer is moved to the 2WD position, both solenoid valve A and B turn on and cham-
ber (a) of the actuator is opened to the atmosphere. At the same time, negative pressure acts on
chamber (b) of the actuator, so that the freewheel clutch is disengaged and 2WD become active.

◇ 4WD
When the transfer is moved to the 4WD position, both solenoid valve A and B turn off and cham-
ber (b) of the actuator is opened to the atmosphere. At the same time, the negative pressure acts
on chamber (a) of the actuator, so that the freewheel clutch is engaged and 4WD becomes ac-
tive.

ON OFF
Fig. 1-37

MMMTC VER 1 MAC17 1 - 20

1. SUPER SELECT 4WD SYSTEM

4. Rear Differential Lock System <Option>
Rear differential lock system has been adopted as optional, and it has the following features.
◇ Locks the right and left wheels completely to facilitate the escape from running off, rocky road, or

snowy road.
◇ Adopts the compact structure with diaphragm to ensure highly reliability for stone chips or freez-

ing.
◇ Adopts the electronic control system. To prevent sudden vehicle behavior and to protect the lock

mechanism, the system refuses the changeover to the differential lock at the speed of 12 km/h or
more even if the differential lock switch is turned ON.
◇ Differential lock changeover is carried out by means of a rear differential lock switch which is locat-
ed on the centre panel.

<Construction Diagram>

Fig. 1-38

<System Component and Function> Functional description
Parts name This automatic restore type switch sends the ON/OFF
signal to the rear differential lock control unit. A rear dif-
Electronic control Rear differential lock ferential lock switch is located on the centre panel.
switch
This lamp is incorporated in the combination meter. It illu-
Rear differential lock minates during operation and flashes during changeover.
Indicator lamp This switch detects the rear differential state: Locked or
Rear differential lock Free. It turns ON/OFF, linked with the move of the differ-
detection switch
This assembly operates linked with ON/OFF of the rear
Air pump assembly differential lock switch. However, it can operate only
when the vehicle speed is less than 12 km/h.
Air piping Transfer control unit
Air hose Based on signals from each switch, this unit operates the
air pump and so on.
Differential lock Rear differential This hose links between the air pump assembly and rear
differential. They transmit air pressure from the air pump

The actuator and pressure plate are housed in the rear
differential, and the rear differential lock detection switch

1 - 21 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM
<Electrical Circuit Diagram>

<Operational Mechanism> Fig. 1-39

Fig. 1-40 When the external air pump assembly op-
erates to transmit air pressure into the ac-
tuator, the pressure plate presses the
drive cam to the driven cam, and both
clutches installed in them engage each
other. The drive cam is engaged with the
differential case and the driven cam is
joined to the side gear (RH), so that the
differential case and side gear (RH) ro-
tates together, and right and left wheels
are locked.

MMMTC VER 1 MAC17 1 - 22

5. Transfer-ECU 1. SUPER SELECT 4WD SYSTEM

Fig. 1-41 The control unit determines the optimum select timing
from the signals received from the various switches and
(1) Terminal Layout sensors, and controls the shift actuators to select the
drive method. In addition, it is also provided with a fail-
safe function and a diagnosis function in case a problem
occurs with the various switches and sensors or with the
shift actuators.
As for vehicles with rear differential lock system, the con-
trol unit controls the rear differential (lock/release).

Fig. 1-42

1 Shift actuator 25 Ignition switch

2- 26 -
3 Shift actuator 27 -

4 Solenoid valve A, B 28 CAN_L

5 4LLc indicator lamp 29 CAN_H

6 Rear differential lock indicator lamp <vehicles 30 Sensor earth
with rear differential lock system>

7 4WD indicator lamp (FL) 31 ASTC-ECU signal (RL)

8 Power supply 32 ASTC-ECU signal (FL)

9 Power supply 41 -

10 Earth 42 Rear differential lock switch (OFF) <vehicles
with rear differential lock system>
11 Earth
12 Front propeller shaft speed sensor 43 Earth <A/T>

44 Transfer lever switch 4H

13 Rear propeller shaft speed sensor 45 Transfer lever switch 4LLc

14 Lever position sensor (LPS) <4M40> 46 2WD/4WD detection switch
15 ASTC-ECU signal (RR) 47 4LLc detection switch

16 ASTC-ECU signal (FR) 48 . Freewheel engage switch

17 - 49 Rear differential lock switch (ON) <vehicles
with rear differential lock system>

18 - 50 Rear differential lock detection switch
<vehicles with rear differential lock system>

19 Air pump assembly <vehicles with rear differ- 51 Transfer lever switch 2H
ential lock system>

20 - 52 Transfer lever switch 4HLc

21 Centre differential lock lamp 53 2WD operation detection switch

22 4WD indicator lamp (FR) 54 4H detection switch

23 2WD indicator lamp (RL) 55 Centre differential lock detection switch

24 2WD indicator lamp (RR) 56 Stop lamp switch

1 - 23 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

(2) Fail-Safe Function
A fail-safe function has been adopted which controls the power transmission if a problem occurs in any
of the switches, sensors or shift actuators or inside the transfer-ECU, in order to maintain the safety of
passengers and the vehicle as the highest priority. In addition, when fail-safe operation is detected,
the centre differential lock indicator lamp or rear differential lock indicator lamp flashes at a rate of 1Hz
as a warning to the driver.

(3) Diagnostic Function
The following function have been provided to make inspection of the Super Select 4WD II sys-
tem and rear differential lock system easier.
◇ Diagnostic trouble code output
◇ Service data output
◇ Actuator test

<Diagnostic Trouble codes>
When diagnostic trouble codes are set, they are stored in the ECU. The diagnostic trouble codes
stored in the ECU (EEPROM) will not be erased even the battery cable is disconnected from the bat-
tery terminal. Furthermore, the diagnostic trouble codes can be read using the MUT-III.

<Service data>
Using MUT-III, the input data and output data to the transfer ECU can be read.

<Actuator test>
The following actuators can be force-driven by sending signals from the MUT-III to the transfer-ECU.
◇ Free wheel engage solenoid valve
◇ Shift actuator
◇ Rear differential lock

(4) 4WD Indicator Lamp
4WD indicator lamps are provided in the combination meter to indicate the driving conditions.

Transfer shift 2H  4H  4HLc  4LLc  4HLc  4H  2H  4HLc  2H
position

4WD indicator Front wheel OFF Flash ON Flash ON Flash ON Flash OFF Flash ON Flash OFF
lamp

C/D lock OFF Flash ON Flash OFF Flash ON Flash OFF
lamp

Rear wheel ON Flash ON Flash ON
lamps
Freewheel OFF ON OFF ON OFF
engage
switch

Detection switches 2WD switch ON OFF ON OFF ON

2WD/4WD ON ON OFF ON OFF ON
switch OFF OFF ON OFF ON OFF

4H switch

C/D lock OFF ON OFF ON OFF
switch OFF ON OFF

4LLc switch

Transfer shift 2H  4H  4HLc  4LLc  4HLc  4H  2H  4HLc  2H
position
Fig. 1-43

MMMTC VER 1 MAC17 1 - 24

1. SUPER SELECT 4WD SYSTEM

(5) Diagnostic Trouble Code Table

ITEM JUDGMENT CONDITION FAIL-SAFE DIAGNOSIS
CODE No.

Transfer shift lever Open circuit/Short cir- Problem with input signal from Control start forbid- C1403
switch system cuit/Malfunction of transfer shift lever switch
den
switch

Diameter tyre of Incorrect tyre pressure/ Front and rear wheel speed differ- Vehicle speed lim- C1405
different Uneven tyre sizes or ence is greater than set value when ited
different brands used the freewheel engage switch is on

Power supply volt- Voltage drop Power supply voltage 9.5 V or lower Control start forbid- C1422
age system den

Overvoltage Power supply voltage 18 V or higher Control cancelled C1423

ASTC-ECU system <Vehicles with ASTC> RAM check error Hold C1450

Lever position Open circuit/Short cir- LPS voltage is lower than 0.2 V Vehicle speed limit C1451
sensor system cuit/Malfunction of sen- when idling
<Vehicles with sor
4M40 Engine>

Front propeller Open circuit/Short cir- Problem with input signal from the Control start forbid- C1452

shaft speed sen- cuit/Malfunction of sen- front propeller shaft speed sensor den

sor system sor

Rear propeller Open circuit/Short cir- Problem with input signal from rear Control start forbid- C1453

shaft speed sen- cuit/Malfunction of sen- propeller shaft speed sensor den

sor system sor

Transfer position Open circuit/Short cir- Transfer selection does not com- Control start forbid- C1454
detection switch cuit/Malfunction of plete while driving den
system switch
Changeover of the transfer is not C1455
completed when the vehicle is
stopped.

Input signal from the transfer posi- Control start forbid- C1456
tion switch is always set on a ran- den
dom basis

Free-wheel en- Open circuit/Short cir- Solenoid valve energization and Control start forbid- C1457
gage solenoid
valve system cuit/Malfunction of so- ECU terminal voltage are not identi- den

lenoid valve cal

Free-wheel en- Open circuit/Short cir- While the vehicle is being driven, Control forbidden C1458
gage switch sys-
tem cuit/Malfunction of the power status of the solenoid

switch valve and the status of the free

wheel engage switch do not match.

Shift actuator sys- Open circuit/Short cir- ECU terminal voltage is higher than Control stopped C1459

tem cuit/Malfunction of ac- main relay voltage (97% of rated

tuator voltage), or lower than main relay

voltage (10% of rated voltage)

Open circuit/Short cir- Actual measurement value for actu- Control stopped C1460

cuit/Malfunction of ac- ator current is 1 A higher than target

tuator value

Open circuit/Short cir- Main relay voltage is 6 V or less Control stopped C1461
C1462
cuit/Malfunction of ac- C1463

tuator Actual measurement value for actu-

ator current is lower than 0.1 A

Open circuit/Short cir- Computation required for driving an Control stopped
cuit/Malfunction of ac- actuator takes more than 5 minutes
tuator

1 - 25 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

(To be continued from the previous page)

ITEM JUDGMENT CONDITION FAIL-SAFE DIAGNOSIS
Rear differential Short circuit/ CODE No.
lock switch system Malfunction of switch When the ON signal from the switch Control stopped C1464
is detected for 60 seconds or more
Rear differential Short circuit/ continuously, or when the ON and C1465
lock air pump as- Malfunction of pump OFF signals from the switch are
sembly system detected at the same time

The terminal voltage is more than 4 Control stopped
V when the pump is not driven, or
the terminal voltage is less than 6 V
when the pump is driven.

Short circuit/ The current value is more than 3 A Control stopped C1466

Malfunction of pump when the pump is driven.

Open circuit/ The current value is less than 0.1 A Control stopped C1468

Malfunction of pump when the pump is driven.

Rear differential Open circuit/Short cir- When the OFF signal from the de- Control stopped C1469
lock engage cuit/Malfunction of tection switch is input for 15 minutes
switch system switch continuously with the rear differen-
tial lock activated, or when the ON
signal from the detection switch is
input for 15 minutes continuously
with the rear differential lock deac-
tivated.

Vehicle discern- Malfunction of ECU When the identification of the in- Hold C1470
ment error stalled engine or transmission is not
the one specified (including the
case when the correct engine ECU
or A/T-ECU is not installed)

Stop lamp switch Open circuit/Short cir- Stop lamp switch is on for 15 Control interrupted C1471

system cuit/Malfunction of minutes or more when driving at a (Centre differential

lamp/Malfunction of vehicle speed of 15 km/h or more lock lamp flickers)

switch

Main relay system Relay problem Voltage is 6.0 V or more, when relayControl cancelled C1541
is OFF C1542
C1607
Voltage is 6.0 V or less when relay
is ON

Transfer-ECU system Malfunction of ECU detected Control stopped

Bus-off U1073
Engine time-out error U1100
Transmission time-out error U1101
ASTC time-out error U1102
Combination meter time-out error U1108
Engine data error U1120
Transmission data error U1121

MMMTC VER 1 MAC17 1 - 26

1. SUPER SELECT 4WD SYSTEM

5. INSPECTION & SERVICE PROCEDURES
1. Transfer Overhaul

Fig. 1-44

Disassembly steps

1 Vacuum hose 16 Steel ball

2 4LLC detection switch 17 Clip

3 Gasket 18 Harness bracket

4 Steel ball 19 Transfer case cover

5 2WD operation detection switch 20 Shift rail drive gear

6 Gasket 21 Shift rail drive gear

7 Steel ball 22 Dust seal guard

8 Center differential lock detection switch 23 Vehicle speed sensor

9 Gasket 24 O-ring
10 Steel ball 25 Rear output sensor
11 4H detection switch 26 O-ring
12 Gasket 27 Front output sensor
13 Steel ball 28 O-ring
14 2WD/4WD detection switch 29 Shift actuator
15 Gasket 30 O-ring
31 Main shaft rail

1 - 27 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

Fig. 1-45

Disassembly steps

32 Rear cover 53 Center differential planetary carrier

33 Oil seal 54 Viscous coupling

34 Snap ring 55 Chain

35 Sensor rotor 56 Front output shaft

36 Steel ball 57 Drive sprocket

37 Oil guide 58 Needle bearing

38 Spacer 59 Synchronizer inner ring

39 Snap ring 60 Synchronizer inner cone

40 Snap ring 61 Synchronizer outer ring

41 Transmission wiring harness protector 62 Synchronizer inner spring

42 Connector bracket 63 Snap ring

43 Connector bracket 64 2-4WD clutch

44 Connector bracket 65 Sun gear

45 Harness bracket 66 Needle bearing

46 Clip 67 Wave spring

47 Connector bracket 68 2-4WD clutch sleeve

48 Chain cover 69 2-4WD shift fork

49 Rear output shaft 70 Spacer

50 O-ring 71 Steel ball

51 Needle bearing 72 Snap ring

52 Snap ring 73 Differential lock hub

MMMTC VER 1 MAC17 1 - 28

1. SUPER SELECT 4WD SYSTEM

Fig. 1-46

Disassembly steps

74 Harness bracket 83 Low speed gear

75 Transfer case plate 84 Needle bearing

76 Needle bearing 85 Rear bearing retainer

77 Countershaft gear 86 Transfer drive shaft

78 Spacer 87 Dust seal guard

79 H-L shift fork 88 Oil seal

80 H-L clutch sleeve 89 Oil pool cover

81 Snap ring 90 Oil guide

82 H-L clutch hub 91 Transfer case

<Synchronizer Ring Installation>

Line up the notched portion of the 2-4WD clutch hub with
the projecting portion of the synchronizer ring and install
the ring on the 2-4WD clutch hub.

Fig. 1-47

1 - 29 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

<Drive Sprocket / Front Output Shaft / Chain Instal-
lation>
1. Set the chain in mesh with the drive sprocket and
front output shaft sprocket and install them in the trans-
fer case.

Fig. 1-48

2. Install the drive sprocket so that its illustrated holes

will mach the projecting portions of the synchronizer
cone.

Fig. 1-49 <Shift Rail Drive Gear Installation>
Install the shift rail drive gear with its marked tooth in
Fig. 1-50
mesh with the third gear groove of the each shift rail.
Fig. 1-51
<Detection Switch Installation>
Fig. 1-52 Install the switches as illustrated.
MMMTC VER 1 MAC17
Mounting Switch Name Tube Connector
Position color color

A 2WD/4WD detection switch Blue Black

B 4LLC detection switch Black Brown

C 2WD operation detection switch Black Black

D 4H detection switch Green White

E Center differential lock detection switch Blue Brown

<Shift Actuator Installation>

Connect a 12 voltage power supply across the terminals
of the actuator connector in a polarity appropriate for
causing the actuator motor to move in the rod extending
direction or retracting direction until the amount of exten-
sion of the rod is as shown in the illustration left.

1 - 30

1. SUPER SELECT 4WD SYSTEM

2. Data List Reference Table

ITEM CHECK ITEM INSPECTION REQUIREMENT NORMAL CON-
NO. DITION
Idling in 1st (Vehicle stopped)
11 Vehicle speed Driving at a constant speed of 50 km/h 0 km/h
Transfer position: 4WD Driving at a constant speed
12 Front propeller shaft speed 50 km/h
sensor of 30 km/h
30 km/h

13 Rear propeller shaft speed Transfer position: 4WD Driving at a constant speed 30 km/h
sensor of 30 km/h

14 Difference between front and Transfer position: 4WD Driving at a constant speed Within 0.37 km/h

rear propeller shaft speeds of 30 km/h

15 Acceleration Idling in 1st (Vehicle stopped) 0G
20 Ignition voltage
21 Power voltage Ignition switch: ON System voltage
22 APS
Ignition switch: ON System voltage
23 APS input
Engine: stopped Accelerator pedal: Fully 1.0 ± 0.05 mV

Transmission gear closed

position: Neutral posi- Accelerator pedal: Depressed Gradually in-
tion creases from the

above value.

Accelerator pedal: Fully open 4.0 V or more

Ignition switch: ON CAN (CAN signal
input) <4M41,
6G7>

24 Engine torque Engine: Accelerate from idling Value (Nm)
25 Shift actuator current Transmission gear position: Neutral position changes
During transfer selection (while motor is running)
0 A → 0.2 A to
1.5 A → 0 A

26 Target current During transfer selection (while motor is running) 0 A → 1.4 A to
1.5 A → 0 A

27 Shift actuator voltage Ignition switch: ON System voltage

28 Air pump motor current (Rear Transmission gear position: Neutral position → 1 V or less →
differential lock)
Transfer shift lever position: 2H→4H→4HLc→4LLc System voltage

(or 4LLc→4HLc→4H→2H)

Ignition switch: ON The air pump motor is acti- Approximately 0.3

Transfer position: vated. A
4WD

Rear differential lock
switch: ON

The rear differential lock is Approximately

kept ON. 0.24 A

1 - 31 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

(Be continued from the previous page)

ITEM CHECK ITEM INSPECTION REQUIREMENT NORMAL CONDI-
NO. TION

29 Air pump motor voltage (rear Ignition switch: ON Rear differential lock switch: System voltage
Transfer position: ON
differential lock) 4WD 1 V or less
Rear differential lock switch:
30 Stop lamp switch Ignition switch: ON OFF ON
31 Stop lamp switch input Engine: stopped Brake pedal: Depressed
OFF
Ignition switch: ON Brake pedal: Released CAN (CAN signal
input) <4M41,
6G7>

H/W (hardwire
signal input)
<4M40>

40 Transfer operating condition Engine: Idling Transfer shift lever position: 2H
(Transfer position)
Transmission gear 2H

position: Neutral posi-

tion

4WD indicator lamp: Transfer shift lever position: 4H
Should not be flash- 4H
ing

41 Transfer shift lever position Ignition switch: ON Transfer shift lever position: 4HLc
(Select mode) Engine: Stopped 4HLc 4LLc
2H
Transfer shift lever position: 4H
4LLc 4HL
4LLc
Transfer shift lever position:
2H

Transfer shift lever position:
4H

Transfer shift lever position:
4HLc

Transfer shift lever position:
4LLc

60 2WD operation detection Driving conditions: 2WD (2H) ON
switch Driving conditions: Other than the above OFF
ON
61 2WD/4WD detection switch Driving conditions: 2WD (2H), 4WD (4H) OFF
ON
Driving conditions: Other than the above OFF
ON
62 4H detection switch Driving conditions: 4WD (4H), 4WD (4HLc)
OFF
Driving conditions: Other than the above ON
OFF
63 Centre differential lock detec- Driving conditions: 4WD (4HLc), 4WD (4LLc) ON
OFF
tion switch Driving conditions: Other than the above ON
OFF
64 4LLc detection switch Driving conditions: 4WD (4LLc)

Driving conditions: Other than the above

65 Transfer lever switch: 2H Transfer shift lever position: 2H

Transfer shift lever position: Other than the above

66 Transfer lever switch: 4H Transfer shift lever position: 4H

Transfer shift lever position: Other than the above

MMMTC VER 1 MAC17 1 - 32

1. SUPER SELECT 4WD SYSTEM

(Be continued from the previous page)

ITEM CHECK ITEM INSPECTION REQUIREMENT NORMAL CONDI-
NO. TION

67 Transfer lever switch: 4HLc Transfer shift lever position: 4HLc ON

Transfer shift lever position: Other than the OFF
above

68 Transfer lever switch: 4LLc Transfer shift lever position: 4LLc ON

Transfer shift lever position: Other than the OFF
above

71 Rear differential lock ON switch Ignition switch: Push the upper part of ON
ON switch

Engine:
stopped

Other than the above OFF

72 Rear differential lock OFF switch Ignition switch: Push the lower part of ON
ON switch

Engine:
stopped

Other than the above OFF

73 Rear differential lock detection switch Ignition switch: The rear differential lock is ON
ON activated.

Engine:
stopped

The rear differential lock is OFF
released.

74 Ignition switch Ignition switch: ON ON

75 Transmission identification Vehicles with M/T M/T

Vehicles with A/T A/T

76 Free-wheel solenoid valve During 2WD ON

During 4WD OFF

77 Free-wheel engage switch During 2WD OFF

During 4WD ON

78 FL ASTC signal Active traction control system is acting on FL ON (Ex. short peri-
wheel od after engine
starts)

79 FR ASTC signal Active traction control system is not acting on OFF
80 RL ASTC signal FL wheel
81 RR ASTC signal Active traction control system is acting on FR ON (Ex. short peri-
82 Neutral switch <A/T> wheel od after engine
starts)
Active traction control system is not acting on OFF
FR wheel
Active traction control system is acting on RL ON (Ex. short peri-
wheel od after engine
starts)
Active traction control system is not acting on OFF
RL wheel
Active traction control system is acting on RR ON (Ex. short peri-
wheel od after engine
starts)
Active traction control system is not acting on OFF
RR wheel
Selector lever position: N ON
Selector lever position: Other than the above OFF

1 - 33 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

3. Actuator Test Table

ITEM CHECK ITEM TEST CONTENTS INSPECTION CON- NORMAL CONDITION
NO. DITIONS

1 Freewheel en- The freewheel engage solenoid Ignition switch: ON The free-wheel engage sole-

gage solenoid valve is driven. Selector lever posi- noid valve condition is turned

valve tion: N over in the actuator test. If

Engine: 0 r/min the freewheel engage sole-
noid valve is ON condition, it

is turned off, and vice versa.

2 Shift actuator Select mode (2H, 4H, 4HLc, 4LLc). Vehicle speed: 0 The mode switches to the

The motor inside the shift actuator km/h (vehicle selected position.
is run in the forward direction.
(MCW) : original position is set at stopped) The motor switches in the
2H.
normal rotation direction

Checked at No.40 (2H→4H→4HLc→4LLc) for 5

T/F operating con- seconds, and it returns to the

dition original position.

The motor inside the shift actuator The motor switches in the
is run in the reverse direction. reverse rotation direction
(MCCW): original position is set at (4LLc→4HLc→4H→2H) for 5
4LLc. seconds, and it returns to the
original position.

3 Rear differen- Activate the rear differential lock air The rear differential lock
switches to ON or OFF.
tial lock pump.

<For Your Reference>

Relation between the selected mode and the detection switch condition is shown in the table below,
refer the table when inspecting the data list items from N.60 to 64.

Data list Select mode

60 2WD operation detection switch 2H 4H 4HLc 4LLc
61 2WD/4WD detection switch ON OFF
62 4H detection switch ON OFF OFF OFF
63 Center differential lock detection switch OFF OFF
64 4LLC detection switch OFF ON OFF ON
OFF ON
ON ON

OFF ON

OFF OFF

MMMTC VER 1 MAC17 1 - 34

1. SUPER SELECT 4WD SYSTEM

6. KNOWLEDGE CHECK
Regarding the following sentences of Super Select 4WD System, identify which ones are correct or
incorrect, and make the required correction to the wrong portion of the incorrect sentence.

(1) The shift actuator is controlled by a switch which works in conjunction with the transfer shift lever
in order to change the vehicle speed.

(2) A planetary gear type centre differential has been adopted which distributes the traction force to
the front and rear output shafts.

(3) The adoption of viscous coupling unit (VCU) makes it possible to distribute the driving force varia-
bly depending on the road condition in 2H mode.

(4) CAN communication has been adopted for communication with other ECUs in order to decrease
the number of wires and improve information transmission.

(5) The operation of the vacuum-driven select system is performed by an integrated transfer select
lever and switch, which allow the driver to select any one of four modes (2H, 4H, 4HLc and 4LLc).

(6) The motor-driven drive mode selection allows the selector lever to be operated smoothly and also
ensures accurate mode selection.

(7) Solenoid valve A, B change the positive pressure route acting on the actuators in accordance with
the signals from the transfer-ECU.

(8) Solenoid valves A, B are turned ON/OFF at the same time.

(9) Freewheel engage switch detects whether the 2WD/4WD mechanism is operating or not operat-
ing.

(10) 4LLc detection switch detects the transfer shift range (Low position) from the High/Low shift rail
position.

(11) 2WD operation detection switch detects the transfer condition (2H position) from the Hi/Low shift
rail position.

(12) 2WD/4WD detection switch detects the transfer condition (2H, 4H position) from the main shift
rail position.

(13) 4H detection switch detects the transfer condition (4H, 4HLc position) from the sub shift rail posi-
tion.

(14) Centre differential lock detection switch detects the transfer condition (4HLc, 4LLc position) from
the main shift rail position.

(15) Front propeller shaft speed sensor detects the rear propeller shaft speed.

(16) Rear propeller shaft speed sensor detects the rear propeller shaft speed.

(17) Shift actuator changes the traction method in accordance with the signal from the ETACS-ECU.

(18) Transfer shift lever switch detects transfer shift lever position.

(19) ETACS-ECU sends traction signals to the various mechanisms based on signals from the vari-
ous switches and sensors.

(20) Transfer-ECU causes the centre differential lock lamp to flash as a warning to the driver when
there is a problem with the system.

1 - 35 MMMTC VER 1 MAC17

SECTION II

Anti-Skid Braking System

CONTENTS

1. GENERAL --------------------------------------------------------------------- 2-1/ 2-3
(1) ABS Function
(2) Slip Ratio
(3) Classification of ABS

2. CONSTRUCTION AND FUNCTION ------------------------------------ 2-4/ 2-8
(1) Construction
(2) Main Components and Functions
(3) ABS Electrical

3. ABS OPERATION ------------------------------------------------------------2-9/ 2-12
(1) ABS Fluid Pressure Control
(2) EBD Fluid Pressure Control
(3) Hydraulic Circuit Operation

4. HYDRAULIC BRAKE BOOSTER (H.B.B) -----------------------------2-13/ 2-18
(1) Features
(2) Fluid Circuit Diagram
(3) Major Components and Function
(4) Hydraulic Circuit Operation

5. SELF-DIAGNOSIS FUNCTION -------------------------------------------2-19/ 2-21
(1) Initial Check
(2) Startup Check
(3) Constant Check
(4) Fail-Safe Function

6. INSPECTION & SERVICE PROCEDURES --------------------------- 2-22/ 2-27
(1) ABS Warning Lamp/ Brake Warning lamp Check
(2) Data List Reference Table
(3) Actuator Test Reference Table
(4) Check of Freeze Frame Data
(5) On-the-Vehicle Inspection
(6) Service Procedures for PAJERO with ABS

7. KNOWLEDGE CHECK ----------------------------------------------------- 2-28

2. ANTI-SKID BRAKING SYSTEM

1. GENERAL
The ABS that ensures directional stability and controllability when applying the brake on the slippery
road surface by preventing the wheel lock respectively, so it can avoid the dangerous situation of ve-
hicle’s skidding and spinning. ABS becomes as standard equipment on almost MMC passenger car
and SUV.

1. ABS Function
Particularly on slippery roads, even the lightest appli-
cation of the brakes can lead to wheel lock-up. The
vehicle doesn’t react to the driver’s steering move-
ments. With ABS the vehicle remains under control so
that it can be steered around an unexpected obstruc-
tion even when the driver has slammed the brakes in
panic.

Without ABS With ABS

Fig. 2-1

Fig. 2-2 Wheel-speed sensors continuously monitor each wheel,
as soon as incipient lock-up is detected at a wheel, ABS
temporarily reduces the braking pressure at the wheel in
question to such a degree that lock-up is prevented.
ABS repeats this monitoring and control cycle in rapid
succession for each wheel.
This form of electronic wheel-slip control ensures opti-
mum braking distances while at the same time maintain-
ing full steer ability and stability.

Notes:
ABS is first and foremost a system that supports driver
braking operation. Therefore, as with vehicles not
equipped with ABS, one must sufficiently decelerate be-
fore a curve since the system was not intended for un-
reasonable driving. Please drive safely.

2. Slip Ratio
ABS controls the wheel speed while applying the brak-
ing. Based on output signals from the wheel speed sen-
sors that are provided each wheels, the ABS-ECU con-
trols the applied brake fluid pressure by actuating the
pressure control solenoid valves. In order to understand
the concept of the wheel speed control, the slip ratio is
essential term to be learned.

Fig. 2-3

2 - 1 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

Vehicle speed is decelerated by the brake force (frictional
force) that acts between the tires and road surface. This is
because wheel speed is reduced by brake application and
a difference produced between the vehicle speed and the
wheel speed. This difference is called slip and expressed
in terms of slip ratio.

Fig. 2-4

<Example>

Fig. 2-6 Fig. 2-5

Fig. 2-7 Brake frictional coefficient μB, side skidding frictional
MMMTC VER 1 MAC17 coefficient μS and slip ratio λ are closely correlated to
one another, and are generally known to have the char-
acteristics as shown in the figure left. The side skidding
frictional coefficient μS is maximized when λ = 0%, and
becomes smaller as the λ becomes larger.
The μB which maximizes the λ is called λopt.
When the wheels are locked, the λ = 100%, the μS ≈
0%, and both the directional stability and steering ability
of the vehicle are lost as shown in the figure left.
In ABS operation the ABS-ECU controls the slip ratio λ
to maintain in around 10 - 30%.

2-2

2. ANTI-SKID BRAKING SYSTEM

3. Classification of ABS

In ABS a hydraulic passage leading from master cylinder to wheel cylinder(s) that has regulating
valve to control the brake pressure is called “channel”.
According to number of the channels and wheel speed sensors to be provided on a vehicle, ABS is
classified the four type as shown in the figure 2-8.

<Front> <Rear>

Regulating Wheel speed sensor
valve
(a) 4-sensor, 4-channels
H line piping model (b) 4-sensor, 3-channels
H line piping model

(c) 4-sensor, 4-channels (d) 3-sensor, 3-channels
X line piping model X line piping model

Fig. 2-8

ABS being adopted on current MMC models have equipped with 4 wheels speed sensors, and is
able to control four wheels speed independently during ABS operation.
However the ABS uses select low control logic commonly, it can be classified as 4-sensors, 3-
channels type ABS.

<Select low control>
In the select-low control, the right and left wheel speeds are compared, and the brake fluid pressure
is controlled for both of the right and left wheel cylinders equally so that is brought in line with a wheel
going to be locked.

2 - 3 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

2. CONSTRUCTION AND FUNCTION <OUTLANDER: CW0W>

The description in this section is based on OUTLANDER (CW0W).

1. Construction
ABS to be adopted on the current models uses a 4-sensor system that controls all four wheels inde-
pendently of each other, and has the following features.
◇ EBD control can obtain ideal rear wheel brake force.
◇ The magnetic encoder for wheel speed detection has been integrated with the wheel hub bearing

instead of the rotor as the wheel speed sensor.
◇ CAN bus has been adopted to communicate with another ECUs.
◇ Fail-safe function which ensures that safety is maintained.
◇ Diagnostic function which provides improved serviceability.

1. Wheel speed sensor

2. Magnetic encoder
3. Stop lamp switch

4. G sensor <4WD>
5. Hydraulic unit
6. ABS warning lamp

7. ABS warning display
8. Brake warning lamp

9. Brake warning display
10. Diagnosis connector
11. ABS-ECU

Fig. 2-9

MMMTC VER 1 MAC17 2-4

2. ANTI-SKID BRAKING SYSTEM
2. Main Components and Functions

Fig. 2-10

Note Dashed lines indicate the CAN bus communication lines.

Name of part Function
Wheel speed sensor
Magnetic encoder Outputs the frequency signal in proportion to the rotation speed of each wheel to ABS-
ECU.
Stop lamp switch
When the magnetic encoder for wheel speed detection (a plate on which north and
south pole sides of the magnets are arranged alternately) rotates, the wheel speed sen-
sor outputs frequency pulse signal in proportion to each wheel speed.

Outputs the signal indicating whether the brake pedal is depressed or not to ABS-ECU.

G sensor <4WD> Incorporated in ABS-ECU, and detects the longitudinal acceleration of the vehicle.

Hydraulic unit Drives the solenoid valve using the signal from ABS-ECU, and controls the brake fluid
ABS warning lamp pressure for each wheel.
ABS warning display
Brake warning lamp Informs the driver of the system status by illuminating, flashing, or turning off the warn-
ing lamp according to the signal from ABS-ECU.

Informs the driver of the system status by illuminating or turning off the warning lamp
according to the signal from ABS-ECU.

Used as the warning lamp for the parking brake, brake fluid level, and EBD control. In-
forms the driver of the system status by illuminating or turning off the warning lamp ac-
cording to the signal from ABS-ECU.

Brake warning display Used as the warning lamp for the brake fluid level, and EBD control. Informs the driver
of the system status by illuminating or turning off the warning lamp according to the sig-
nal from ABS-ECU.

ABS-ECU - Outputs the diagnosis code and establishes the communication with MUT-III.
- Controls actuators based on the signals coming from each sensor.
- Controls the self-diagnosis and fail-safe functions.
- Controls the diagnosis function (MUT-III compatible).

2 - 5 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

3. ABS Electrical

Fig. 2-11

(1) Wheel Speed Sensor
The wheel speed detecting section 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 (Hall element
semiconductor sensor). This sensor outputs frequency pulse signals in proportion to the wheel
speed.

MMMTC VER 1 MAC17 Fig. 2-12
2-6

2. ANTI-SKID BRAKING SYSTEM

The front wheel speed detecting section 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.

Fig. 2-13

Weight Silicon (2) G Sensor <4WD model only>
beam The G-sensor is incorporated in ABS-ECU, and detects
longitudinal acceleration of a vehicle.
Detect the displacement As the all wheels are driven for 4WD vehicles, the ABS-
value of the weight ECU is hard to estimate the vehicle speed only based
on the wheel speed sensor outputs. Because the front
Inertia force wheels and rear wheels are connected through the pro-
peller shaft, so the brake force applied on one wheel
may affect the other thee wheel speeds, then the all
wheel speeds are going to be lowered simultaneously.
In cope with the vehicle speed estimation, the 4WD ve-
hicle equips with G sensor.

<Principal of G sensor>
Minute beam which is made by silicon supports the
weight. The silicon beam can detect the weight dis-
placement, which is happen by acceleration force, as an
electric signal.

Acceleration force
Fig. 2-14

2 - 7 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

(3) ABS Warning Lamp/ Brake Warning Lamp

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

*: The ABS warning lamp and the brake warning

lamp stay on until the ignition switch is turned to

Not the LOCK (OFF) position.
e When the brake fluid level in the brake fluid reser-
voir tank is lower than the specified value, or when

the parking brake lever is pulled, the brake warning

lamp turns ON.

Fig. 2-15

State ABS warning lamp Brake warning lamp
Correct
Normal ABS failure --
Faulty EBD failure
Actuator not operated Illuminates -
When MUT-III is Actuator operated
connected After the actuator is activated forcibly * Illuminates Illuminates

--

Flash (2Hz) -

Illuminates* Illuminates*

Fig. 2-16 (4) ABS-ECU
By integrating ABS-ECU into the hydraulic unit, no wir-
ing harness for sending drive signal of the solenoid
valve and pump motor is required, assuring higher relia-
bility.
By incorporating the G-sensor, no sensor harness is re-
quired, enhancing the reliability.
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 func-
tion and illuminates the ABS warning lamp and brake
warning lamp.

The brake warning lamp is used as the EBD con-
Note trol warning lamp.

ABS-ECU detects vehicle speed from the signals of the
wheel speed sensor and its incorporated G sensor, rec-
ognizes 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.

MMMTC VER 1 MAC17 2-8

2. ANTI-SKID BRAKING SYSTEM

3. ABS OPERATION <OUTLANDER: CW0W>
The description in this section is based on OUTLANDER (CW0W).

1. ABS Fluid Pressure Control
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 <4WD> 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 increas-
es, 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 deter-
mines 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 deter-
mines 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).

Solenoid valve
operation

Vehicle and
wheel deceler-
ation velocity

Wheel cylinder
hydraulic pres-
sure

Fig. 2-17

2 - 9 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

2. EBD Fluid Pressure Control EBD (Electronic Brake force Distribution) fluid
pressure control is activated in a range with lower
Fig. 2-18 slip ratio where ABS is not activated. EBD calcu-
lates vehicle deceleration and slip amount of the
four wheels based on the wheel speed sensor sig-
nal. If the rear wheel speed differs from the vehicle
speed by a certain level or more, EBD increases,
holds, and decreases the brake fluid pressure at
the rear wheels and controls solenoid valves in the
hydraulic unit in order to adjust the rear wheel
brake fluid pressure fairly close to an ideal distri-
bution curve.

Fig. 2-19 EBD control is a control system which provides a
Effect of EBD high level of control for both vehicle braking force
and vehicle stability. The system has the following
features:
◇ Because the system provides the optimum

rear braking force regardless of the vehicle
laden condition of the road surface, the sys-
tem reduces the required pedal depression
force, particularly when the vehicle is heavily
laden or driving on road surfaces with high
frictional coefficients.
◇ Rear brake power is electronically controlled

to optimize performance and to ensure opti-
mal distribution of braking force between the
front and rear brakes. Then the duty placed
on the front brakes has been reduced, the in-
creases in brake pad temperature can be con-
trolled during front brakes applying to improve
the wear resistance characteristics of the disc
brake pad.
◇ Rear brake fluid pressure control employs a

ABS hydraulic unit that made it possible to
eliminate the mechanical pressure control
valves (proportioning valves).

MMMTC VER 1 MAC17 Fig. 2-20
2 - 10

2. ANTI-SKID BRAKING SYSTEM

3. Hydraulic Circuit Operation
(1) Ordinary Braking Mode
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 pres-
sure 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

IN OFF Opened

OUT OFF Closed

Brake fluid flow during pedal depressed

Brake fluid flow during pedal released
Fig. 2-21

(2) 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 solenoid valves and causes the valves to be ener-
gized. As a result, the solenoid valves IN close, blocking the fluid passage from the master cylin-
der. The solenoid valves OUT, on the other hand, open, clearing the fluid passage from the wheel
cylinders to the reservoir. 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

IN ON Closed

OUT ON Opened

Brake fluid flow
Fig. 2-22

2 - 11 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

(3) 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-energized. 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 cylin-
ders.

Solenoid valve Current supply Valve position

IN ON Closed

OUT OFF Closed

Brake fluid flow

Fig. 2-23

(4) Pressure Increasing Mode

When the ABS-ECU determines that none of the wheels are approaching lock-up, it stops current
supply to the solenoid valves. As a result, all the solenoid valves are de-energized, and the fluid in
the master cylinder flows through solenoid valve IN to the wheel cylinders to apply greater pres-
sure.

Solenoid valve Current supply Valve position

IN OFF Opened

OUT OFF Closed

Brake fluid flow
Fig. 2-24

MMMTC VER 1 MAC17 2 - 12

2. ANTI-SKID BRAKING SYSTEM

4. HYDRAULIC BRAKE BOOSTER (HBB) <PAJERO: V80W/V90W>
The most of MMC vehicles equip the vacuum type brake booster, Master Vac. excluding PAJERO
with ABS. The description in this section is the hydraulic brake booster employed on PAJERO.
1. Features
A hydraulic brake booster system (HBB) has been adopted to improve the braking performance.
◇ With having the independent power source (pump motor), the system has the following features.

1. Has its own power source, so that a stable power supply can be maintained at all times regard-
less of the engine condition.

2. The need for a negative pressure line from the engine has been eliminated.
◇ With the hydraulic assist, the system has the following features.

1. Quick response to emergency braking.
2. Compared to the vacuum brake booster which requires large capacity, it is smaller in size.
◇ The master cylinder, the reservoir and the hydraulic unit are integrated as one unit for fewer
pipes.

2. Fluid Circuit Diagram
The master cylinder hydraulic pressure for the front brakes is assisted by a brake booster which uti-
lizes accumulator pressure; the hydraulic pressure generated by the accumulator is led directly to the
rear brakes.

Fig. 2-25 MMMTC VER 1 MAC17
2 - 13

2. ANTI-SKID BRAKING SYSTEM

3. Major Components and Function

Name of part Outline of function
ABS-ECU
Controls the HBB system.

HBB buzzer and Operates and illuminates in response to signals from the ABS-ECU to notify the driver of

brake warning lamp any abnormalities in the HBB system.

Pump motor The pump motor pumps up brake fluid from reservoir and charges high-pressure brake
Accumulator fluid to the accumulator.

The accumulator is pressurized with nitrogen gas and accumulates the hydraulic pres-
sure which is generated by the pump motor.

Switching solenoid During the ABS control, the regulator pressure is introduced to the wheel cylinder.
valve (built into hy-
draulic unit)

Control solenoid valve Controls (increase, maintain, or decrease) the wheel cylinder hydraulic pressure when
(built into hydraulic ABS operates.
unit)

Pressure switch (built Two switches are included: a switch for pump control and a switch for low-pressure warn-
into hydraulic unit) ing control. The former switch outputs a pump motor drive signal when the accumulator

hydraulic pressure drops below the specified hydraulic pressure. If the accumulator pres-
sure drops further, the low-pressure warning control switch turns off so that a warning
lamp illumination signal and an HBB buzzer operating signal are output.

Relief valve (built into This is a mechanical valve which is used to prevent excessively high pressure from build-

hydraulic unit) ing up in the power supply system. If the pump motor keeps operating continuously be-

cause of a problem such as a pressure switch malfunction, this valve allows excess

brake fluid to be returned to the reservoir.

Master cylinder The master cylinder is a single-piston type which generates hydraulic pressure which is
transmitted to the front brakes.

Brake booster Converts the accumulator high pressure into a pressure which corresponds to the brake
pedal depression force, and transmits this to the rear brakes, and also to the booster
chamber to generate the brake assist force.

Reservoir Stores the brake fluid for the master cylinder and the power supply.

Brake fluid level warn- When the level of brake fluid inside the reservoir drops, this switch turns on and causes
ing switch (built into the brake warning lamp to illuminate.
reservoir)

(1) Pump Motor, Accumulator, Pressure switches, HBB buzzer

Hydraulic unit
(built-in pressure switches)

Fig. 2-26

MMMTC VER 1 MAC17 2 - 14

Fig. 2-27 2. ANTI-SKID BRAKING SYSTEM

An electric pump motor (piston type) has been adopted. The
accumulator is pressurized with nitrogen gas and collects the
hydraulic pressure which is generated by the pump motor.
When the accumulator hydraulic pressure drops to approxi-
mately 16 MPa or below, the pressure switch (for pump con-
trol) turns off, and a pump motor drive signal is output from
the ABS-ECU to make the pump motor operate. When the
pump motor operates, it pressurizes the brake fluid, which is
discharged through the check valve to be stored in the accu-
mulator. The operation described above generates the hy-
draulic pressure (high pressure) which is required for normal
brake operation and also HBB, EBD and ABS operations.
When the accumulator hydraulic pressure drops to approxi-
mately 11 MPa or below, the pressure switch (for low pressure
warning) turns off, and this causes the brake warning lamp to
illuminate and the HBB buzzer to sound. Then, when the ac-
cumulator hydraulic pressure rises to approximately 17 MPa,
the pressure switch (for pump control) turns on, and after ap-
proximately 1 second, the pump motor stops opening. If there
is a malfunction of the pressure switch at this time, the release
valve opens when the pressure reaches approximately 24
MPa to prevent excessive pressure from building up.

Fig. 2-28

(2) Master Cylinder, Brake Booster

Fig. 2-29

◇ The master cylinder is a single piston type with a centre valve, and it controls only the front brakes.

◇ The brake booster has an integrated structure which envelopes the master cylinder at the front
and rear. The front section consists of a regulator piston, a return spring, a spool valve for switch-
ing the brake fluid line, a reaction rod and a reaction disc which changes shape in response to the
pressure in that order, and the rear section consists of an operating rod, a power piston and a
booster chamber in that order.

◇ The operating rod and the power piston are directly linked, and the regulator piston which trans-
mits the pedal operating force and the spool valve are also directly linked.

◇ The force from the master cylinder is applied to the regulator piston in the forward direction (to the
left in the illustration), and the power assist force from the booster is applied to the regulator piston
in the reverse direction (to the right in the illustration). This produces a balance between the two
via the reaction disc, so that a hydraulic pressure is generated which is proportional to the pedal
depression force.

◇ The regulator piston is equipped with a return spring to maintain the spool return force when there
is no power assist force being applied by the booster.

2 - 15 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

<Booster operation>

Fig. 2-30

1. When the pedal operating force is transmitted in turn by the operating rod, the power piston and
the master cylinder piston, the regulator piston and the spool valve move to the left.

2. When the spool valve opens line A and closes line B, the accumulator pressure is supplied to the
rear brakes. This pressure is introduced to the booster chamber and provides power assistance to
move the master cylinder piston to the left.

3. Then, when the pressure in the booster chamber increases, the pressure which is applied to the
rear (left side) of the reaction disc also increases, and the reaction disc starts to change shape.
The reaction disc contacts the reaction rod, and the reaction rod in turn contacts the spool valve,
so that the master cylinder pressure being applied towards the left and the booster pressure being
applied to the right are brought into balance by the reaction disc. This allows the power-assist hy-
draulic pressure generated by the pedal operating force to be kept at an equilibrium.

Note: When a loss of accumulator pressure occurs
If a loss of accumulator pressure occurs because of a problem such as a pump motor problem, the
power assist force and rear brake pressure cannot increase in response to the input from the brake
pedal. Accordingly, the front brakes can be operated directly by depressing the brake pedal, but the
rear brakes do not operate at all.

Fig. 2-31 (3) Reservoir, Brake Fluid Level Warning Switch

The reservoir is equipped with brake fluid supply ports
for the pump motor and for the master cylinder and
brake booster, and return ports for returning the brake
fluid from the booster and the various solenoid valves.
In addition, the brake fluid level warning switch which is
built into the reservoir detects the brake fluid level, and
causes the brake warning lamp to illuminate when the
fluid level drops below a specified level.

MMMTC VER 1 MAC17 2 - 16

2. ANTI-SKID BRAKING SYSTEM

4. Hydraulic Circuit Operation

(1) Normal Braking
During normal braking, the switching solenoid valves and the control solenoid valves are not ener-
gized, so that the hydraulic pressure generated by the HBB master cylinder passes straight through
the switching solenoid valve and the front control solenoid valves (IN) to act on the front brakes.
In case of the rear brakes, the EBD control function of the ABS-ECU operates the rear control sole-
noid valves to carry out the pressure increase, the pressure hold and the pressure decrease opera-
tions in order to control the brake pressure to the ideal levels. The rear brakes are acted upon by the
hydraulic pressure which is generated by the HBB.

Switching
solenoid

valve

Fig. 2-32

2 - 17 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

(2) When ABS is Operating
If it appears that the vehicle wheels may lock up at times such as during sudden braking, the ABS-
ECU operates the control solenoid valves as described below, repeatedly activating the pressure in-
crease, the pressure hold and the pressure decrease modes to control the brake pressure being ap-
plied to the wheels which are showing a tendency to lock. At the same time, the switching solenoid
valves (for FL and FR) are also energized during ABS operation. When the switching solenoid valves
are turned on, the hydraulic pressure passage connecting on the front brakes is switched the one
from the master cylinder to the one from HBB accumulator (boost pressure). This can reduce the
brake pedal kickback force which is generated during ABS operation.

Switching
solenoid valve

Fig. 2-33

<Pressure Decrease Mode>
The control solenoid valve (IN) turns ON and the fluid line from the master cylinder is interrupted. At
the same time, the control solenoid valve (OUT) also turns ON and the fluid line from the wheel cylin-
der to the reservoir is opened so that the hydraulic pressure inside the wheel cylinder is reduced.

<Pressure Hold Mode>
The control solenoid valve (IN) turns ON and the control solenoid valve (OUT) turns OFF, the both
fluid lines of one from the master cylinder to the wheel cylinder and the other one from the wheel cyl-
inder to the reservoir are interrupted. As the result, the hydraulic pressure inside the wheel cylinder is
maintained at the current pressure.

<Pressure Increase Mode>
Both control solenoid valves (IN and OUT) turns OFF, the hydraulic pressure from the master cylin-
der is supplied to the wheel cylinder to increase the pressure in the wheel cylinder.

MMMTC VER 1 MAC17 2 - 18

2. ANTI-SKID BRAKING SYSTEM

5. SELF-DIAGNOSIS FUNCTION <OUTLANDER:CW0W >

The description in this section is based on OUTLANDER (CW0W).
1. 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 illuminating the ABS warning lamp and disables
ABS control.

Note The ABS warning lamp may stay on after the ignition switch is turned ON until the
startup vehicle 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).

2. 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 opera-
tion.

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.

3. 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 out-
put 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.
(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.

<Diagnostic Function with MUT-III>
ABS-ECU has the following functions for easier system checks. The following items can be diag-
nosed using MUT-III.
◇ Diagnosis code set

◇ Service data output

◇ Actuator test

◇ Freeze frame data output

2 - 19 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

<Diagnosis Code Chart>

During diagnosis, a diagnosis code associated with other system may be set when the ignition

Caution switch is turned on with connector(s) disconnected. On completion, confirm all systems for diagno-

sis code(s). If diagnosis code(s) are set, erase them all.

Diagnosis Item 9.7 ± 0.3 V or less
code No. 18.0 ± 1.0 V or more
C100A Abnormality in FL wheel speed sensor circuit
C1015 Abnormality in FR wheel speed sensor circuit Abnormality in output voltage
C1020 Abnormality in RL wheel speed sensor circuit Abnormality in output voltage
C102B Abnormality in RR wheel speed sensor circuit
C1011 Abnormality in FL wheel speed sensor signal
C101C Abnormality in FR wheel speed sensor signal
C1027 Abnormality in RL wheel speed sensor signal
C1032 Abnormality in RR wheel speed sensor signal
C1014 Mutual monitoring of FL wheel speed sensor
C101F Mutual monitoring of FR wheel speed sensor
C102A Mutual monitoring of RL wheel speed sensor
C1035 Mutual monitoring of RR wheel speed sensor
C1041 Abnormality in periodical signal for FL wheel speed sensor
C1042 Abnormality in periodical signal for FR wheel speed sensor
C1043 Abnormality in periodical signal for RL wheel speed sensor
C1044 Abnormality in periodical signal for RR wheel speed sensor
C1046 FL wheel speed sensor control phase time exceeded
C1047 FR wheel speed sensor control phase time exceeded
C1048 RL wheel speed sensor control phase time exceeded
C1049 RR wheel speed sensor control phase time exceeded
C104B Abnormality in FL wheel inlet valve system
C104F Abnormality in FR wheel inlet valve system
C1053 Abnormality in RL wheel inlet valve system
C1057 Abnormality in RR wheel inlet valve system
C105F Abnormality in FL wheel outlet valve system
C1063 Abnormality in FR wheel outlet valve system
C1067 Abnormality in RL wheel outlet valve system
C105B Abnormality in RR wheel outlet valve system
C2104 Faulty valve power supply circuit
C1073 Faulty motor drive circuit
C2116 Abnormality in power supply voltage in pump motor
C1000 Abnormality in stop lamp switch circuit
C2200 Abnormality in ABS-ECU
C2100*1 Abnormality in battery voltage (low voltage)

C2101 Abnormality in battery voltage (high voltage)
C1395 Brake fluid filling not complete
C2203 Chassis No. not programmed
C1210*2 Abnormality in G
C1242*2
Abnormality in G
C1608
U0001 Implausible diagnosis data
U0100 Bus off
U0114*2 Engine time-out error
4WD-ECU time-out error
U0141
U1415 ETACS time-out error
U1417 Variant coding not completed
Variant coding value invalid (includes faulty installation)

MMMTC VER 1 MAC17 2 - 20

2. ANTI-SKID BRAKING SYSTEM

4. 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. And the brake warning lamp is
used as EBD control warning lamp.

Diagnosis code Item Countermeasures for failure

EBD control ABS control
Executed*3
C100A Abnormality in FL wheel speed sensor circuit Prohibited
C1015
C1020 Abnormality in FR wheel speed sensor circuit
C102B
C1011 Abnormality in RL wheel speed sensor circuit
C101C
C1027 Abnormality in RR wheel speed sensor circuit
C1032
C1014 Abnormality in FL wheel speed sensor signal Executed*3 Prohibited
C101F
C102A Abnormality in FR wheel speed sensor signal
C1035
C1041 Abnormality in RL wheel speed sensor signal
C1042
C1043 Abnormality in RR wheel speed sensor signal
C1044
C1046 Mutual monitoring of FL wheel speed sensor Executed*3 Prohibited
C1047
C1048 Mutual monitoring of FR wheel speed sensor
C1049
C104B Mutual monitoring of RL wheel speed sensor
C104F
C1053 Mutual monitoring of RR wheel speed sensor
C1057
C105F Abnormality in periodical signal for FL wheel speed sensor Executed*3 Prohibited
C1063
C1067 Abnormality in periodical signal for FR wheel speed sensor
C105B
C2104 Abnormality in periodical signal for RL wheel speed sensor
C1073
C2116 Abnormality in periodical signal for RR wheel speed sensor
C1000
C2200 FL wheel speed sensor control phase time exceeded Executed*3 Prohibited
C2100*1
FR wheel speed sensor control phase time exceeded
C2101
C1395 RL wheel speed sensor control phase time exceeded
C2203
C1210*2 RR wheel speed sensor control phase time exceeded
C1242*2
Abnormality in FL wheel inlet valve system Prohibited Prohibited
C1608
U0001 Abnormality in FR wheel inlet valve system
U0100
U0114*2 Abnormality in RL wheel inlet valve system

U0141 Abnormality in RR wheel inlet valve system
U1415
U1417 Abnormality in FL wheel outlet valve system Prohibited Prohibited

Abnormality in FR wheel outlet valve system

Abnormality in RL wheel outlet valve system

Abnormality in RR wheel outlet valve system

Malfunction of valve power supply circuit Prohibited Prohibited
Executed Prohibited
Malfunction of motor drive circuit Executed Prohibited
Executed Executed
Abnormality in pump motor power supply voltage Prohibited*4 Prohibited*4

Abnormality in stop lamp switch circuit Executed Prohibited
Prohibited Prohibited
Trouble in ABS-ECU Prohibited Prohibited
Executed Prohibited
Battery voltage problem (low voltage) 9.7 ± 0.3 V or less Executed Executed
8.0 ± 0.5 V or less Executed Prohibited

Battery voltage problem (high voltage) 18.0 ± 1.0 V or more Executed Prohibited

Brake fluid charging incompletion Executed Executed
Executed Executed
VIN not written Executed Executed
Executed Executed
Abnormality in G-sensor output voltage
Executed Executed
Abnormality in G-sensor output signal Executed Prohibited
Executed Prohibited
Implausible diagnosis data

Bus off

Engine time-out error

4WD-ECU time-out error

ETACS time-out error

Variant coding not implemented

Invalid variant coding value (including wrong assembly)

Note *1: This diagnosis code is not set within the vehicle speed of 20 km/h or less.
*2: 4WD.
*3: Prohibited when two or more wheels are faulty.
*4: Not prohibited when the brake warning lamp is not illuminated.

2 - 21 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

6. INSPECTION & SERVICE PROCEDURES

1. ABS Warning Lamp/ Brake Warning Lamp Check <OUTLANDER: CW0W>
Check that ABS and brake warning lamps illuminate as follows.

Note The EBD warning lamp is also used as the brake warning lamp.

1. When the ignition switch is turned to the ON position,
ABS and brake warning lamps illuminate.
2. The ABS and brake warning lamps illuminate for three
seconds*1 and then turn OFF*2.
3. Otherwise, check the diagnosis code.

Note *1: The ABS warning lamp may stay ON until the vehicle
speed reaches 10 km/h. As far as ABS-ECU stores
any diagnosis code related to the wheel speed sensor
malfunction or the motor malfunction as past trouble,
ABS-ECU continues illuminating the ABS warning
lamp until it verifies that the malfunction for that code
is resolved (startup check).

*2: The brake warning lamp does not turn OFF when the
parking brake is applied or the brake fluid level is low-
ered.

Fig. 2-34

2. Data List Reference Table <OUTLANDER: CW0W>
The following items can be read by the MUT-III from the ABS-ECU input data.

Note While ABS-ECU is disabled by the diagnostic function, the MUT-III displayed data is different from
the actual measurement.

Item No. Check item Check conditions Normal conditions

1 FL wheel speed sensor Perform a test run of the vehicle. The speedometer display and the MUT-III

2 FR wheel speed sensor display almost agree with each other.
3 RL wheel speed sensor (During stop: approximately 0.7km/h)

4 RR wheel speed sensor

5 Power supply voltage System voltage (10 to 18 V, ABS opera-
tional range)

7 Brake switch (input) The brake pedal is released. OFF

The brake pedal is depressed. ON

9 G sensor <4WD> Vehicle stopped (level) -0.11 to 0.11 G

Running -1 to 1 G

14 Brake switch (Stop light The brake pedal is depressed. ON

switch) The brake pedal is released. OFF

87 Ignition switch (input) Ignition switch is "ON" position ON

88 Vehicle speed Perform a test run of the vehicle. The speedometer display and the MUT-III
display almost agree with each other.

105 Power supply voltage (input) System voltage (10 to 18 V, ABS opera-
tional range)

MMMTC VER 1 MAC17 2 - 22

2. ANTI-SKID BRAKING SYSTEM

3. Actuator Test Reference Table <OUTLANDER: CW0W>
Using MUT-III, the following actuators can be forcibly operated:

Note ◇ ABS is operated by ABS-ECU.

◇ When ABS-ECU is disabled due to the fail-safe function, the actuator test cannot be performed.

◇ The actuator test can be performed only when the vehicle is stationary.

◇ While the actuator test is performed, the ABS warning lamp flashes at a rate of 2 Hz.

◇ After the actuator test has been performed, the brake warning lamp and ABS warning lamp illumi-
nate until the ignition switch is turned to ON again or the communication between MUT-III and ABS
-ECU is terminated.

Item No. Check item Driven component
Solenoid valve for the corresponding wheel of the hydraulic unit and
01 FR wheel ABS drive pump motor (simplified inspection mode)

Operation pattern of items 01 to 04

02 FL wheel ABS drive

03 RR wheel ABS drive

04 RL wheel ABS drive

4. Check of Freeze Frame Data <OUTLANDER: CW0W>

The freeze frame data can be checked by using the MUT-III. When detecting fault and storing the
diagnosis code, the ABS-ECU stores the ECU status of that time as the freeze frame data. By ana-
lyzing each of them, the troubleshooting can be performed more efficiently. The displayed items are
as the table below.

No. Item name Data item Unit
1 Odometer Total driving distance after the diagnosis code is generated km

2 Ignition cycle Number of times the ignition switch is turned "ON" or "LOCK Number of
(OFF)" after the past failure transition counts is
displayed.
4 Accumulated minute Cumulative time for current malfunction of diagnosis code
5 Power supply voltage Voltage of power supply when the diagnosis code is generated min

V

13 Stop lamp switch Stop lamp switch condition when the diagnosis code is generated: -
OFF/ON

301 ABS control ABS control when the diagnosis code is generated: OFF/ON -

401 FL wheel speed sensor Wheel speed (FL) when the diagnosis code is generated km/h

402 FR wheel speed sensor Wheel speed (FR) when the diagnosis code is generated km/h

403 RL wheel speed sensor Wheel speed (RL) when the diagnosis code is generated km/h

404 RR wheel speed sensor Wheel speed (RR) when the diagnosis code is generated km/h

Note ◇ *1: This diagnosis code is not set within the vehicle speed of 20 km/h or less.
◇ *2: 4WD.

2 - 23 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

5. On the Vehicle Inspection <OUTLANDER: CW0W>
(1) Hydraulic Unit Check
1. Raise the vehicle using a jack and support the specified points with a rigid rack.
2. Connect MUT-III to the vehicle.
3. Confirm that the selector lever is in the "N" position, and then start the engine.
4. When carrying out the actuator tests No. 01 to 04, perform the actuator tests using MUT-III while
depressing the brake pedal. When carrying out the actuator tests, rotate the wheel by hands to con-
firm that the braking force changes.

Note ◇ While performing the actuator test, the ABS warning lamp flashes at a rate of 2 Hz.

◇ When ABS-ECU is disabled due to the fail-safe function, the M.U.T.-III actuator test cannot be
performed.

◇ After the actuator test has been performed, the ABS warning lamp and brake waning lamp illumi-
nate until the ignition switch is turned to ON again or the communication between M.U.T.-III and
ABS-ECU is terminated.

(2) In the Event of a Discharged Battery

Warning If the ABS is not operating, the vehicle posture will be unstable during braking. Do not drive the ve-
hicle with the ABS-ECU connector disconnected or with the ABS not operating for any other reason.

If the engine is started using a booster cable when the battery is completely flat, and the vehicle is
then driven without waiting for the battery to be recharged, the engine may misfire and it may not be
possible to drive the vehicle. This is because the ABS consumes a large amount of current when car-
rying out its initial checks. If this happens, recharge the battery fully.

(3) Inspection of Component

<Wheel Speed Sensor Current Check>

◇ Do not connect the battery terminals in reverse as the wheel speed
sensor may be damaged.

Caution ◇ When the current value is measured by the wheel speed sensor

connector, measure it with the wheel speed sensor installed in the
vehicle.

1. Connect the circuit tester to the wheel speed sensor using the special
tool extra fine probe (MB992006), and measure the sensor current as a
single unit.
Standard value: 5.9 to 8.4 mA or 11.8 to 16.8 mA
2.If the measurement value is not within the standard value range, re-
place the wheel speed sensor with a new one.

Fig. 2-35

<Wheel Speed Sensor Insulation Check>

1. Connect the circuit tester to the wheel speed sensor using the special
tool extra fine probe (MB992006), and measure the insulation resistance
between the terminal No. 1/2 and the wheel speed sensor body as a sin-
gle unit.
Standard value: 5 MΩ or more

2. If the insulation resistance is not within the standard value range, re-
place the wheel speed sensor with a new one.

Fig. 2-36 2 - 24
MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

6. Service Procedures <PAJERO: V80W/V90W>
(1) Hydraulic Brake Booster (HBB) Operation Check

Caution Turn the ignition switch ON, and wait for at least 120 seconds before carrying out the
checks.

1. Turn the ignition switch to the LOCK (OFF) position. Depressurize the power supply system of the
hydraulic brake booster (HBB) by depressing the brake pedal at least forty times until the pedal
effort becomes high.

2. Check that the reservoir fluid level is at the MAX position.

3. Chock the wheels and release the parking brakes.

4. Turn the ignition switch ON, and measure how much time is elapsed after the pump motor starts
until it stops.

Standard value: 20 - 80 seconds

5. After the pump motor stopped, start the engine. The brake warning lamp should not be turned on.

6. Stop the engine, and then turn on the ignition switch again.

7. When the brake pedal is depressed four or five times, the pump motor should start and then stop.

8. Depress the brake pedal four or five times again, and then measure how much time is elapsed
after the pump motor starts until it stops.

9. Depress the brake pedal fully consecutive 15 - 20 times for ten seconds. The brake warning lamp
should illuminate and the buzzer should sound.

Standard value: 2 - 11 seconds

A diagnosis code may be stored when carrying out the checks. Always erase the diagnosis
Caution codes after the checks, and then check that any diagnosis code is set.

(2) Air Bleeding

Caution Specified brake fluid: DOT 3 or DOT 4
◆ Always use the specified brake fluid. Avoid using a mixture of the specified brake fluid

and other fluid.
◆ Maintain the fluid reservoir level between the MIN and MAX marks during the air

bleeding.
◆ Do not depress the brake pedal hard during the air bleeding (normal air bleeding) to

prevent the pump motor from operating frequently.
◆ After the air bleeding, check that the brake dragging does not become stronger.

◆ If the pedal is depressed with the reservoir cap removed, the brake fluid may overflow.

Do not depress the brake pedal while the fluid is being added.

<Normal Air Bleeding>

After the front brake or the rear brake is removed and installed, some fluid may remain in the hydraulic
brake booster (HBB) reservoir. In this case, bleed air from the brake caliper.

2 - 25 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

<HBB System Air Bleeding>

If all the brake fluid inside the reservoir is drained due to the removal and installation of the HBB,
bleed air as follows:
1. -Air bleeding from front brake system-
Turn the ignition switch to the LOCK (OFF) position. Bleed air from the front brake calipers (right and
left) by pumping the brake pedal.

2. -Pump motor operation-
Turn the ignition switch ON, and operate the pump motor. If the pump motor is running free, supply the
brake fluid into the pump motor by depressing the brake pedal three or four times.

3. -Air bleeding from accumulator system-

1) After the pump motor stopped, depress the brake pedal three or four times with the ignition switch
ON. Then observe the brake fluid in the reservoir. If the brake fluid looks whitish, wait for a few
minutes until it becomes clear.
2) Repeat the step 1) until the brake fluid becomes clear.

4. -Air bleeding from rear brake system-

◆ If too much brake fluid is drained at a time, the accumulator pressure may be dropped
abnormally. So limit drain amount at a time to 100 cm3 or less, and check that the

Caution ◆ pump motor stops per one air-bleeding.
If the brake fluid level in the reservoir has been dropped, air may enter the pump motor

accidentally. To avoid this, always maintain the brake fluid between the MIN and MAX

marks.

While the ignition switch is turned ON and the brake pedal is depressed, bleed air from the right and
left rear brake calipers.

5. -Air bleeding from power supply system-

1) Turn the ignition switch to the LOCK (OFF) position. Depressurize the HBB power supply system
by depressing the brake pedal several times until the braking effort becomes high.
2) Turn the ignition switch ON, and depress the brake pedal quickly twenty times. Then check that
the pump motor stops.
3) Turn the ignition switch to the LOCK (OFF) position. Depressurize the power supply system of
the hydraulic brake booster (HBB) by depressing the brake pedal until the pedal effort becomes
high.

4) Then turn the ignition switch ON, and then operate the pump motor. The pump motor should stop
within 25 seconds. If the pump motor does not stop, bleed air from the power supply system again
[see steps 1) - 4)].

6. -Air bleeding from ABS system-

Caution Turn the ignition switch to the LOCK (OFF) position when connecting and disconnecting
the MUT-III.

1) Turn the ignition switch to the LOCK (OFF) position, and connect the MUT-III to the diagnosis
connector.
2) Turn the ignition switch ON, and then select the menu display on the MUT-III as follows:
’’ABS/ASC’’ to ’’ACTUATOR TEST’’ to ’’AIR BLEEDING (1).’’

Caution If you carry out the ’’AIR BLEEDING (1)’’ repeatedly, wait for at least twenty seconds
before the second operation.

3) While the ignition switch is turned ON and the brake pedal is depressed, carry out the actuator
test ’’AIR BLEEDING (1).’’
4) Then select "AIR BLEEDING (2)" on the M.U.T.-III menu display, and carry out the "AIR BLEED-
ING(2)" while the ignition switch is turned ON and the brake pedal is depressed.

MMMTC VER 1 MAC17 2 - 26

2. ANTI-SKID BRAKING SYSTEM

7. -Air bleeding from rear brake system (final stage)-

Caution ◆ If too much brake fluid is drained at a time, the accumulator pressure may be
dropped abnormally. So limit drain amount at a time to 100 cm3 or less, and check
that the pump motor stops per one air-bleeding.

◆ If the brake fluid level in the reservoir has been dropped, air may enter the pump

motor accidentally. To avoid this, always maintain the brake fluid between the MIN
and MAX marks.

Bleed air from the rear brake calipers completely while the ignition switch is turned ON and the brake
pedal is depressed.

8. -Air bleeding from front brake system (final stage)-
Operate the pump motor while the ignition switch is turned ON. Bleed air from the front brake calipers
completely by pumping the brake pedal.

9. -Adding brake fluid-
1) Turn the ignition switch to the LOCK (OFF) position. Depressurize the power supply system of the
hydraulic brake booster (HBB) by depressing the brake pedal at least forty times until the pedal effort
becomes high.
2) Add the brake fluid up to the MAX mark on the reservoir.

2 - 27 MMMTC VER 1 MAC17

2. ANTI-SKID BRAKING SYSTEM

5. KNOWLEDGE CHECK
Regarding the following sentences of Anti-skid Braking System, identify which ones are correct or
incorrect, and make the required correction to the wrong portion of the incorrect sentence.

(1) The ABS that ensures fuel economy when applying the brake on the slippery road surface by pre-
venting the wheel lock respectively.

(2) The ABS can avoid the dangerous situation of vehicle’s skidding and spinning during braking.

(3) ABS being adopted on current MMC models have equipped with 4 wheels speed sensors, howev-
er the select high control logic is used, then it can be classified as 4-sensors, 3-channels type ABS.

(4) EBD (Electronic Brake-force Distribution system) control can obtain ideal rear wheel brake force.

(5) In the ABS employed on PAJERO (V80W/V90W), the hydraulic unit function is integrated into the
vacuum brake booster (VBB).

(6) In the ABS employed on PAJERO (V80W/V90W), the switching solenoid valve is adopted to im-
prove operation feeling by reducing the pedal kickback force while the ABS operates.

(7) ABS controls the engine speed while applying the braking based on output signals from the crank
angle sensor that are provided each wheels.

(8) The ABS-ECU controls the applied brake fluid pressure by actuating the pressure control solenoid
valves.

(9) The wheel speed is reduced by brake application and the difference is produced between the en-
gine speed and the wheel speed. This difference is called slip and expressed in terms of slip ratio.

(10) The side skidding frictional coefficient μS is maximized when λ = 0%, and becomes smaller as
the λ becomes larger.

(11) The ABS-ECU controls the slip ratio λ to maintain in around 60 - 80% so that the μB shows the
maximized value in ABS operation.

(12) When the wheels are locked, the λ = 100%, the μS ≈ 0% and the μB is very low. In this situation,
both of the directional vehicle stability and steering ability are lost.

(13) Wheel speed sensor used on OUTLANDER (CW0W) sends alternative current signals at fre-
quencies which are proportional to the rotation speeds of each wheel to the ABS-ECU.

(14) In ABS used on OUTLANDER (CW0W), solenoid valve power source circuit incorporated in the
ABS-ECU controls the power supply to the solenoid valves.

(15) ABS warning lamp informs the driver of the system status by flash, illuminating or turning off the
warning lamp according to the signal from Engine-ECU.

(16) Stop lamp switch sends a signal to the ABS-ECU to indicate whether the brake pedal is de-
pressed or not.

(17) Hydraulic Brake Booster system (HBB) has been adopted on PAJERO (V80W/V90W) with ABS
to improve the braking performance. The HBB has the independent power source (vacuum chamber)
so that a stable power supply can be maintained at all times regardless of the engine condition.

(18) Control solenoid valve to be built into the hydraulic unit controls the wheel cylinder hydraulic
pressure in the 3 stages (increase, maintain, or decrease) when ABS operates.

(19) If a loss of the HBB accumulator pressure occurs due to some failure, the rear brakes can be
operated directly by depressing the brake pedal, but the front brakes do not operate at all.

(20) EBD control is activated in a range with lower slip ratio where ABS does not cover. EBD adjusts
rear wheel brake fluid pressure fairly close to an ideal distribution curve.

MMMTC VER 1 MAC17 2 - 28

SECTION III

Active Stability
Control System