E Textbook Power Train & Chassis M2

CONTENTS

1. GENERAL -------------------------------------------------------------------- 3-1/ 3-5
(1) Outline of TCL Function
(2) Outline of Stability Control Function
(3) Outline of Hill Start Assist (HAS) Function

2. ELECTRONIC CONTROL SYSTEM ----------------------------------- 3-6/ 3-13
(1) Main Components and Functions
(2) Schematic Diagram
(3) ASC Electrical Diagram
(4) Sensors
(5) Actuators
(6) ASC-ECU

3. SYSTEM OPEARATION -------------------------------------------------- 3-14/ 3-21
(1) Traction Control Operation
(2) Stability Control Operation
(3) HAS Operation
(4) Hydraulic Circuit Operation

4. INSPECTION & SERVICE PROCEDURES -------------------------- 3-22/ 3-29
(1) On-Vehicle Service
(2) Data List Reference Table
(3) Actuator Test Table

5. KNOWLEDGE CHECK ----------------------------------------------------- 3-30

3. ACTIVE STABILITY CONTROL SYSTEM

1. GENERAL
The ASC system integrates the traction control (TCL) function and stability control function.
◇ When TCL detects the slip of the driving wheel (ex. during startup on low µ road), it automatically

applies the brakes to the slipping driving wheel. At the same time, TCL reduces the engine out-
put and prevents the wheel spin when it determines that the engine torque is too high for the
road surface µ.
◇ When the ASC-ECU determines that the vehicle is in a dangerous condition, it reduces the en-
gine output and applies brake force to four wheels independently to control the vehicle behavior,
avoiding the critical state.
◇ Hill Start Assist (HSA) function has been adopted to hold and prevent the roll back of the vehicle
on a slope while the foot is transferred from the brake pedal to the accelerator pedal <Vehicles
with HSA>.

(1) Outline of TCL Function
When the driving wheels slip on the slippery road surface, TCL applies the brake automatically,
sends the signal requesting engine torque reduction to the Engine-ECU, and prevents the loss of the
driving force resulting from the slippage of the driving wheel.

In the figure 3-1 one wheel is placed on the slippery road surface.
In case of a vehicle without TCL, the wheel on the slippery road will spin and the traction force of the
other wheel will reduce while accelerating.
In case of a vehicle with TCL, the system prevents the wheel from spinning by applying the brake
force. It prevents the other wheel from losing traction force and ensures vehicle stability and steering
ability when driving off and accelerating.
Each wheel speed sensor is continuously and individually monitored, and TCL analyzes the sensor
signals and recognizes immediately when a wheel might spin. In this situation TCL electronically con-
trols the brake force to be applied on the spinning wheel, and requests to the Engine-ECU to reduce
engine torque.

Brake force

Traction force Low frictional road surface

Vehicle without TCL Vehicle with TCL

Fig. 3-1

3 - 1 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

B’ <Principle and Benefit of TCL>
B Like ABS, TCL controls the slip ratio where the driving
force and side force of the tires can be performed as
Note: maximum according to vehicle operating and road con-
(A), (B) --- Characteristics on slippery road surface ditions by controlling the tire slip ratio (differential ratio
(A’), (B’) --- Characteristics on asphalt paved road between vehicle and wheel speeds).
While a vehicle is in motion, the tires develop a driving
Fig. 3-2 force for acceleration and side force for turning. The fig-
ure 3-2 shows the relationship between these two forces
and the side slip.

(1) The driving force (‘A) and the side force (‘B) on as-
phalt or similar paved road show larger than that on slip-
pery road surface (A) and (B).

(2) The slip ratio control is carried out according to vehi-
cle motions as follows;
Straight-ahead motion:
Region (I) with a relatively higher slip ratio
Turning motion:
Region (II) with a relatively lower slip ratio

Vehicle with TCL can ensure better acceleration perfor-
mance as shown in the figure 3-3 under start-off condi-
tion with fully accelerated.

Steering wheel angle Time (sec.) The figure 3-4 shows the directional stability when the

(deg.) Fig. 3-3 vehicles start off with fully accelerated on a gravel cov-
ered slope. The vehicle with TCL has a superior direc-
Time
tional stability so that the required steering wheel angle
Fig. 3-4 adjustment to maintain the straight-ahead direction is
much less than that of vehicle without TCL. So drivers

can operate the vehicle with TCL with less effort and
stress.

MMMTC VER 1 MAC17 3-2

3. ACTIVE STABILITY CONTROL SYSTEM

Fig. 3-5 <Traction Control for PAJERO>

Some models of PAJERO have adopted M-ATSC
(Mitsubishi Active Stability and Traction Control Sys-
tem). As one of M-STAC function, the active traction
control automatically applies braking force to the free-
wheeling drive wheels caused by driving on the partially
low-friction efficiency road surface and improper contact
of wheels with the road so that loss of driving power
caused by the freewheeling drive wheels can be pre-
vented.
For example of the figure 3-5, when the vehicle is driv-
ing off road, application of braking force to the free-
wheeling front left and rear right wheels can give driving
power to not freewheeling front right and rear left wheels
so that evacuation capability equivalent to differential
lock can be provided.

While descending rough road, there is also chance that
a wheel may lose the contact with the ground and cause
the freewheeling, then the engine brake force will be
lost. Braking force is automatically applied to the spin-
ning lifted wheel in order to ensure the engine braking
working. This function is called the engine braking assist
control, and it can be activated under the following con-
ditions.
- Drive mode: 4LLC
- Transmission: 1st gear
- Service brake: Not be applied

3 - 3 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

(2) Outline of Stability Control Function
ASC-ECU detects vehicle movement based on information from various sensors and calculates a
model of ideal vehicle movement. ASC-ECU compares the actual vehicle movement with the ideal
vehicle model, and manages the brake of the specific wheel so that the actual vehicle movement
gets close to the ideal vehicle mode. It also controls the understeer or oversteer condition by creating
the yaw moment in the vehicle.

<Stability Control Operation>
The stability control manages the vehi-
cle attitude by creating a yaw moment
from altering the balance between the
cornering force and each wheel’s
brake mechanism.

Fig. 3-6 <Effect of Stability Control>
Fig. 3-7
For example, on a slippery surface, if
the vehicle tends to be under-steered

contrary to the driver’s intention, a yaw
moment (a rotational moment) is creat-
ed to restrain the under-steering by
increasing the rear-inside braking
force. On the other hand, when the
vehicle tends to be oversteered, a yaw
moment (a restorative moment) is cre-
ated to restrain the oversteering by
increasing the front-outside wheel
braking force. Furthermore, when it is
determined that the vehicle is over-
speeding, safe and stable cornering is
enabled by deceleration from reducing
the engine output.

MMMTC VER 1 MAC17 3-4

3. ACTIVE STABILITY CONTROL SYSTEM

(3) Outline of Hill Start Assist (HSA) Function
The Hill Start Assist (HSA) automatically holds the brakes applied to help prevent the vehicle from
rolling backwards during the time it takes the driver to release the brake pedal and apply the acceler-
ator when the vehicle is stopped on a steep slope.

Without HSA With HSA

Fig. 3-8

<Operation>

(State 1) Prerequisite for the HSA operation

- Vehicle comes to standstill at a steep slope with depressing brake pedal.
- Active stability control system detects a standstill at a steep slope from the sensors in the

system and the CVT-ECU.
(State 2) Holding brake force by the ASC hydraulic unit

- The ASC holds braking force after that releasing the brake pedal (Brake holding duration is
2 seconds as maximum) or until stepping on the accelerator pedal.

(State 3) Start off
- When depressed accelerator pedal, the ASC releases brake force relating with engine torque
increase.

Brake force is maintained. Brake force decreases by depressing
Brake force decreases by accelerator pedal.
releasing brake pedal.

Brake

Brake pe- ON Brake pedal is
OFF released.

Vehicle speed

Engine

Accelerator
pedal

State State 2 State
Fig. 3-9

3 - 5 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

2. ELECTRONIC CONTROL SYSTEM
(1) Main Components and Functions
The active stability control system is composed of the following parts as shown below.

1. Wheel speed sensor 9. ABS warning lamp 17. Engine-ECU
2. Magnetic encoder
3. Stop lamp switch 10. ABS warning display 18. CVT-ECU
4. G & Yaw rate sensor
5. Steering wheel sensor 11. Brake warning lamp 19. A/T-ECU
6. ASC OFF switch
7. Brake fluid pressure switch 12. Brake warning display 20. 4WD-ECU
8. Hydraulic unit
13. ASC operation display and lamp 21. AWC-ECU

14. ASC OFF display 22. ASC control unit (ASC-ECU)

15. ASC warning display and lamp

16. Diagnosis connector

Fig. 3-10

MMMTC VER 1 MAC17 3-6

3. ACTIVE STABILITY CONTROL SYSTEM

Name of part Functional description

Wheel speed sensor Outputs the frequency signal in proportion to the rotation speed of each wheel to ASC-
ECU.

Magnetic encoder for The wheel speed sensor is a pulse generator. When the magnetic encoder for wheel
wheel speed detection speed detection (a plate on which north and south pole sides of the magnets are ar-

ranged alternately) rotates, it outputs frequency pulse signal in proportion to each wheel
speed.

Stop lamp switch Outputs the signal indicating whether the brake pedal is depressed or not to ASC-ECU.

G & yaw rate sensor Detects longitudinal and lateral acceleration of a vehicle, and outputs signal to ASC-
ECU via the CAN line.

Steering wheel sensor Detects the steering angle of the steering wheel, and outputs signal to ASC-ECU via the
CAN bus line.

ASC OFF switch Outputs the ON/OFF signal for TCL/ASC to ASC-ECU.

Brake fluid pressure Integrated into the hydraulic unit, and outputs the signal for the brake fluid pressure in

sensor the master cylinder to ASC-ECU.

Hydraulic unit Drives the solenoid valve using the signal from ASC-ECU, and controls the brake fluid
pressure for each wheel.

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

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

Brake warning lamp Used as the brake warning lamp for the parking brake, brake fluid level, and EBD con-
trol. Informs the driver of the system status by illuminating or turning off the brake warn-
ing lamp according to the signal from ASC-ECU.

Brake warning display Used as the brake warning display for the brake fluid level, and EBD control. Informs the
driver of the system status by illuminating or turning off the brake warning display ac-
cording to the signal from ASC-ECU.

ASC operation display Informs the driver of the system status by flashing when the system operates according

and lamp to the signal from ASC-ECU.

ASC OFF display Informs the driver of the system shutdown by illuminating by the signal from ASC-ECU.
Informs the driver that the brake system overheats and the brake TCL stops by flashing
the ASC OFF display for the duration of approximately 2 Hz.

ASC warning display TCL function and stability control function, HSA function uses the same display and
and lamp lamp. Depending on the signal from ASC-ECU, the ASC warning display and lamp in-
forms the driver of the system status by illuminating when the system has malfunction
(When the ASC warning display and lamp is illuminated, the HSA function does not op-
erate).

Diagnosis connector Sets the diagnosis code and establishes the communication with MUT-III.

Engine-ECU Controls the engine output based on the signal from ASC-ECU.

CVT-ECU - CVT-ECU performs integrated control with ASC-ECU.
- Output the gear position to ASC-ECU.

A/T-ECU - A/T-ECU performs integrated control with ASC-ECU.
- Output the gear position to ASC-ECU.

4WD-ECU - Outputs the drive status to ASC-ECU.
- 4WD-ECU performs integrated control with ASC-ECU.

AWC-ECU - Outputs the drive status to ASC-ECU.
- AWC-ECU performs integrated control with ASC-ECU.

ASC control unit (ASC- - Controls the actuators (hydraulic unit) based on the signals sent from sensors.

ECU) - Controls the self-diagnostic function and fail-safe function.

- Controls diagnostic function (Compatible with MUT-III).

3 - 7 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

(2) Schematic Diagram
The outline of electrical wiring composed of the ASC system is shown below.

Fig. 3-10

Note Dashed lines indicate the CAN bus line.

Fig. 3-11

MMMTC VER 1 MAC17 3-8

3. ACTIVE STABILITY CONTROL SYSTEM
(3) ASC Electrical Diagram

Fig. 3-12
3 - 9 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

(4) Sensors

<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
(semiconductor sensor). This sensor outputs frequency pulse signals in proportion to the wheel
speed.
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. 3-14 Fig. 3-13
Fig. 3-15
<G & Yaw Rate Sensor>
The G & yaw rate sensor is installed under the front
floor console, and detects the yaw rate, lateral and lon-
gitudinal <except for 2WD> acceleration of the vehicle.

<Steering Wheel Sensor>
The steering wheel sensor is attached to the column
switch, and detects the rotational angle of the steering
wheel.

MMMTC VER 1 MAC17 3 - 10

3. ACTIVE STABILITY CONTROL SYSTEM

Fig. 3-16 <ASC OFF Switch>

The ASC OFF switch is attached on the instrument pan-
el to the outside of the driver’s seat. ASC functions can
be disabled by pressing this switch for 3 seconds (The
HSA function operates even when the ASC system is
turned OFF with the ASC OFF switch). Pressing this
switch again resumes the ON status. As a countermeas-
ure for the stuck of the ASC OFF switch, pressing the
ASC OFF switch for 15 seconds resumes the system to
the ON status.
When the ignition switch is turned from "LOCK" (OFF) to
ON position, TCL and stability control functions are con-
stantly in the ON status.

- ASC OFF Switch Operation and System Operation -

ASC OFF switch operation TCL HSA
Brake control Engine control Stability control
Enabled
Not operated Enabled Enabled Enabled Enabled

Operated (Press and hold for 3 seconds) Prohibited Prohibited Prohibited

Note The stability control is available when the vehicle speed is 15 km/h or more.

3 - 11 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

ABS warning lamp Brake warning lamp ASC operation/ (5) Actuators
warning lamp <Display and lamp>
ASC OFF display The ASC system illuminates or flashes the ASC opera-
tion display and lamp, ASC warning display and lamp,
Information display or ASC OFF display in the following operation patterns,
and informs the driver of the ASC system status.
- ASC operation display and lamp -

Flashes in 2 Hz during the ASC control.
- ASC warning display and lamp -

Turns ON when the system malfunction occurs.
- ASC OFF display -

ASC-ECU detects the overheat of the brake pads.
When the brake TCL control is prohibited,

the ASC OFF display flashes in approximately 2 Hz.

Fig. 3-17

State ASC operation ASC warning dis- ASC OFF dis-
display and lamp play and lamp play

Normal Normal - - -
Flashing (2 Hz) - -
Stability control operated Flashing (2 Hz) - -
- - Illuminates
TCL operated
- - Flashing (2 Hz)
ASC is disabled by ASC disabled
ASC OFF switch - Illuminates Illuminates
- Illuminates Illuminates
When the brake pad ASC-ECU informs the driver that - Illuminates -*
temperature is high the brake TCL does not function. - - -
- Illuminates Illuminates
Abnormal Stability control malfunction

TCL malfunction

HSA malfunction

MUT-III connection Actuator not operated

Actuator operated

Note * Illuminates if the TCL function or stability control function is defective when the HSA function is
defective. (HSA control prohibited)

<Hydraulic Unit>

The hydraulic unit incorporates the ABS control and ASC control. The cut valve, pressure relief valve,
suction valve, suction damper, and pressure sensor have been added to the unit for the ASC control.

MMMTC VER 1 MAC17 3 - 12

3. ACTIVE STABILITY CONTROL SYSTEM

(6) ASC-ECU

This ECU incorporates the ABS function, EBD function,
stability control function, HSA function, and TCL func-
tion. The hydraulic units of the ASC and TCL systems
employ the automatic pressurization function. These
systems also incorporates G and yaw rate sensor,
steering wheel sensor, and master cylinder pressure
sensor (integrated with hydraulic unit).

Fig. 3-18 <Integrated Control>

ASC transmits data necessary for control of ABS and
TCL, performing joint control.

Control system Control content

ABS Even during ABS operation, ABS performance is improved from the joint operation of the

stability control.

TCL During acceleration, engine output is governed through joint operation with stability con-
trol.

<Fail-Safe and Diagnostic Functions>
ASC-ECU constantly monitors the input and output signals. If an error is detected in the system, ASC
-ECU sends a fail signal and the corresponding indicator lamp is illuminated or blinks. Various con-
trols are processed depending on the cause of malfunction as shown below.
ASC-ECU has the following functions for easier system checks.
◇ Diagnosis code set
◇ Service data output
◇ Actuator test
◇ Freeze frame data output
◇ All the above items can be diagnosed using MUT-III.

<Calibration>
After the G & yaw rate sensor and steering wheel sensor have been replaced with new ones, calibra-
tion must be performed using MUT-III.

3 - 13 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

3. SYSTEM OPERATION
(1) Traction Control Operation
ASC-ECU receives various kinds of information from Engine-ECU, steering wheel sensor, G and yaw
rate sensor, wheel speed sensor, AWC-ECU, A/T-ECU, CVT-ECU, and 4WD-ECU. When ASC-ECU
determines that the driving wheel is slipping, it suppresses the wheel slippage. At this time, ASC-
ECU controls the brake fluid pressure of the driving wheel determined to be slipping so that the
torque is transferred to another driving wheel. Basically, the operations of ABS solenoid valve and
ASC valve are the same. ASC-ECU, Engine-ECU, steering wheel sensor, G and yaw rate sensor,
wheel speed sensor, AWC-ECU, A/T-ECU, CVT-ECU, and 4WD-ECU communicate with each other
via the CAN bus line. When the accelerator pedal is depressed too far, the signal requesting the en-
gine speed reduction is sent to Engine-ECU. The ASC-ECU performs integrated control with A/T-
ECU or CVT-ECU and secures the TCL controllability.

(2) Stability Control Operation
ASC-ECU receives various kinds of information from Engine-ECU, ETACS-ECU, CVT-ECU, A/T-
ECU, 4WD-ECU, AWC-ECU, steering wheel sensor, G and yaw rate sensor, and wheel speed sen-
sor. When ECU determines the vehicle runs in the oversteer or understeer direction based on the
signal sent from these sensors and ECUs, ASC-ECU drives each valve and pump motor and controls
the braking force to be applied to the wheels.
When the system increases the fluid pressure automatically, it closes the cut valve to shut off the
pressure line to the suction valve, and drives the pump motor. For example, when the vehicle runs in
the understeer direction while turning to the right, ASC-ECU supplies the brake fluid from the pump to
the rear right wheel to apply the braking force on it.
ASC-ECU and Engine-ECU communicate with each other via CAN. When the accelerator pedal is
depressed too far, the signal requesting the engine output reduction is sent to Engine-ECU.

(3) HSA Operation
ASC-ECU receives various kinds of information from Engine-ECU, G and yaw rate sensor, CVT-
ECU, A/T-ECU, ETACS-ECU and wheel speed sensor. When the ASC-ECU judges that the vehicle
is stopped on a steep slope, the HSA maintains the brake wheel cylinder pressure while the driver
releases the brake pedal and then depresses the accelerator pedal, to prevent the vehicle from slid-
ing down the slope. The next time the accelerator pedal is depressed, the maintained brake wheel
cylinder pressure is released depending on the engine torque.

<System Configuration>

MMMTC VER 1 MAC17 Fig. 3-19
3 - 14

3. ACTIVE STABILITY CONTROL SYSTEM
<HSA Function State Transition Diagram (Overview)>

Fig. 3-20

◇ HSA Function control Activated
ASC-ECU judges that the HSA operation condition is satisfied. When the driver releases the
brake pedal, ASC-ECU maintains the brake wheel cylinder pressure and waits.

◇ Fluid Pressure Hold Mode
By closing the cut valve, ASC-ECU maintains the brake wheel cylinder pressure of the time when
the brake pedal is depressed, to prevent the vehicle from moving backward.

◇ Start Mode
ASC-ECU releases the brake wheel cylinder pressure maintained by the cut valve, depending on
the engine torque generated by depressing the accelerator pedal.

◇ Forcible Termination Mode
ASC-ECU immediately releases the brake wheel cylinder pressure maintained by the cut valve
and terminates HSA function control.

Note ASC-ECU judges the inclination angle of the slope according to the G and yaw rate sensor output.
When either of the following conditions is satisfied, the mode is shifted to the forcible termination
mode, and HSA function control is terminated.
The parking brake operation is detected.
The shift or selector lever operation to the shift position other than the uphill direction driving is de-
tected (Forward uphill driving: shift or selector position other than "D", Reverse uphill driving: shift or
selector position other than "R").
The accelerator pedal and brake pedal are depressed at the same time.
The wheel speed sensor pulse is generated (When the vehicle moved)
The engine is stopped by engine stall, etc.
As for vehicles with M/T, only during forward uphill driving, the HSA operates even when the shift
lever is in the N position.

3 - 15 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

(4) Hydraulic Circuit Operation

<Brake fluid pressure is applied> --- Stability Control, TCL

The system closes the cut valve to block the passage from the pump outlet to the master cylinder,
and opens the suction valve, connecting the passage from the master cylinder to the pump inlet. The
brake fluid from the master cylinder is supplied to the wheel cylinder.

- Valve Condition -

Item Power status Open/Close

Cut valve ON Closed

Suction valve ON Open

Inlet valve* OFF Open

Outlet valve* OFF Closed

Note Fig. 3-21

* The inlet valve and the outlet valve close or open depending on driving conditions to control
the brake fluid pressure at each wheel.

MMMTC VER 1 MAC17 3 - 16

3. ACTIVE STABILITY CONTROL SYSTEM

<Brake fluid pressure is held> --- Stability Control, TCL, HAS

The system closes the cut valve, suction valve and outlet valve to hold the brake fluid pressure in the
wheel cylinder.

- Valve Condition -

Item Power status Open/Close

Cut valve ON Closed

Suction valve OFF Closed

Inlet valve* OFF Open

Outlet valve* OFF Closed

Note Fig. 3-22

* The inlet valve and the outlet valve close or open depending on driving conditions to control
the brake fluid pressure at each wheel.

3 - 17 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

<Brake fluid pressure is decreased> --- Stability Control, TCL

The system opens the outlet valve while closing the inlet valve to store the brake fluid filled in the
wheel cylinder in the low pressure accumulator. The brake fluid stored in the low pressure accumula-
tor returns to the master cylinder through the suction valve.

- Valve Condition -

Item Power status Open/Close

Cut valve OFF Open

Suction valve OFF Closed

Inlet valve* ON Closed

Outlet valve* ON Open

Note Fig. 3-23

* The inlet valve and the outlet valve close or open depending on driving conditions to control
the brake fluid pressure at each wheel.

MMMTC VER 1 MAC17 3 - 18

3. ACTIVE STABILITY CONTROL SYSTEM

<Reference Information>

The active stability control system also has incorporated ABS function, and the hydraulic circuit oper-
ation of ABS is shown as follows.

◆ Brake fluid pressure decrease

Brake fluid supplied from the wheel cylinder is stored in the low pressure accumulator. Then, the
stored brake fluid is returned to the master cylinder by driving the pump using the motor.

- Valve Condition -

Item Power status Open/Close
Open
Cut valve OFF Closed
Closed
Suction valve OFF Open

Inlet valve ON

Outlet valve ON

Fig. 3-24

3 - 19 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

◆ Brake fluid pressure is held

The system closes the inlet valve and outlet valve to hold the brake fluid pressure in the wheel
cylinder. If the brake fluid is stored in the low pressure accumulator, the brake fluid is returned to
the master cylinder by driving the pump using the motor.

VALVE CONDITION

Item Power status Open/Close

Cut valve OFF Open

Suction valve OFF Closed

Inlet valve ON Closed

Outlet valve OFF Closed

Fig. 3-25

MMMTC VER 1 MAC17 3 - 20

3. ACTIVE STABILITY CONTROL SYSTEM

◆ Brake fluid pressure is increased

The system opens the inlet valve while closing the outlet valve to increase the brake fluid pres-
sure in the wheel cylinder.

- Valve Condition -

Item Power status Open/Close

Cut valve OFF Open

Suction valve OFF Closed

Inlet valve OFF Open

Outlet valve OFF Closed

Fig. 3-26

3 - 21 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

4. INSPECTION AND SEVICE PROCEDURES

(1) On-Vehicle Service
<Hydraulic Unit Check>
1. Raise the vehicle using a jack and support the specified points with a rigid rack.
2. Before setting MUT-III, turn the ignition key to the LOCK (OFF) position.
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 No.05 to 08, perform the actuator
tests using MUT-III without depressing the brake pedal. When carrying out the actuator tests, rotate
the wheel by hands to confirm that the braking force changes.

Note While performing the actuator test, the ABS warning lamp flashes at a rate of 2 Hz.
When ASC-ECU is disabled due to the fail-safe function, the MUT-III actuator test cannot
be performed.
After the actuator test has been performed, the ABS warning lamp, brake waning lamp,
ASC ON indicator lamp, and ASC OFF indicator lamp illuminate until the ignition switch is
turned to ON again or the communication between MUT-III and ASC-ECU is terminated.

5. This is indicated as shown in the figure 3-25.

Fig. 3-27

6. When any malfunction has been found, take a necessary action according to the "Judgment Ta-
ble."

Display on MUT-III Operation Test result Judgment Cause Measure
-
Depress the brake Braking force Normal -
pedal to lock the
wheel. decreases for 3

seconds from the

lock status.

Select the vehicle to The wheel does Error Clogged brake line Check and

be inspected using not lock even if other than hydrau- clean the brake

MUT-III, perform the the brake pedal is lic unit line.

actuator test. depressed.

01 FL wheel ABS Rotate the selected Clogged hydraulic Replace the
02 FR wheel ABS wheel by hands to
03 RL wheel ABS confirm the braking circuit in the hy- hydraulic unit
04 RR wheel ABS force.
draulic unit assembly.

Braking force Faulty routing of Route the brake
does not de- hydraulic unit tube correctly.
crease. brake tube

Malfunction of hy- Replace the
draulic unit sole- hydraulic unit
noid valve opera- assembly.
tion

MMMTC VER 1 MAC17 3 - 22

3. ACTIVE STABILITY CONTROL SYSTEM

Display on MUT-III Operation Test result Judgment Cause Measure

Select the vehicle to Lock condition Normal --
be inspected using occurs for 3 sec-
MUT-III, perform the onds from the
actuator test. status without
braking force.
Rotate the selected
05 FL wheel TCL wheel by hands to
06 FR wheel TCL confirm the braking
07 RL wheel TCL force.
08 RR wheel TCL
The wheel does Error Faulty routing of Check and
not lock.
hydraulic unit clean the brake

brake tube line.

Clogged brake line
other than hydrau-
lic unit

Clogged hydraulic Replace the

circuit in the hy- hydraulic unit

draulic unit assembly.

7. After the inspection, turn the ignition switch to the LOCK (OFF) position, and then disconnect MUT-
III.

<All Sensor Calibration (G and Yaw Rate Sensor, Steering Wheel Sensor, Brake Fluid Pres-
sure Sensor)>

Caution Before carrying out the calibration, check that the diagnosis code related to the steering
wheel sensor, G and yaw rate sensor, or brake fluid pressure sensor is not set.

When the next operation has been completed, carry out the calibration to make ASC-ECU

Caution learn the neutral point of the steering wheel sensor, G and yaw rate sensor, and brake fluid
pressure sensor.

◆ ASC-ECU replacement

Carry out the calibration under the following conditions.

Caution ◆ The vehicle has one occupant (driver) only.
◆ Turn the steering wheel to set the wheels in the straight-ahead positions.

◆ The brake pedal is not depressed. (The stop lamp switch is OFF.)

1. Park the vehicle on a level surface.
2. Turn the ignition key to the LOCK (OFF) position, and connect MUT-III to the vehicle.
3. Turn the ignition switch to the ON position.
4. Select "ABS/ASC/ASTC."
5. Select "Special function."
6. Select "Sensor calibration."
7. Select "all sensor calibration."
8. Turn the ignition key to the LOCK (OFF) position, and remove MUT-III from the vehicle.

<G and Yaw Rate Sensor Calibration>

Caution Before performing calibration, check that the G and yaw rate sensor-related diagnosis code
is not set.

After the next operation has been completed, carry out the calibration to make ASC-ECU

Caution learn the neutral position of the G and yaw rate sensor.
◆ G and yaw rate sensor replacement

◆ ASC-ECU replacement

3 - 23 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

1. Park the vehicle on a level surface.
2. Turn the ignition key to the LOCK (OFF) position, and connect MUT-III to the vehicle.
3. Turn the ignition switch to the ON position.
4. Select "ABS/ASC/ASTC."
5. Select "Special function."
6. Select "Sensor calibration."
7. Select "Lateral G sensor calibration."
8. Select "G sensor calibration."
9. Turn the ignition key to the LOCK (OFF) position, and remove MUT-III from the vehicle.

<Steering Wheel Sensor Calibration>

After the next operation has been completed, carry out the following two operations:
1. Update the neutral position stored in the steering wheel sensor.
2. Reset the calibrated value of the steering angle stored in ASC-ECU.

Caution ◆ Alignment adjustment <Front>
Steering wheel sensor (column switch assembly) replacement, removal, installation
◆ ASC-ECU replacement
◆ When the steering wheel sensor is replaced or installed, perform "Steering angle cor-
◆ rection amount initialization" of the AWC-ECU.

◆ Before performing the calibration, check if the steering wheel sensor-related diagnosis
code is set in ASC-ECU.
Caution When the diagnosis code other than C121A is set, carry out inspection according to

◆ each troubleshooting procedure.

1. Park the vehicle on a level surface with tires and steering wheel positioned in a straight ahead di-
rection.
2. Turn the ignition key to the LOCK (OFF) position, and connect MUT-III.
3. Turn the Ignition switch to ON.
4. Select "Steering angle sensor."
5. Select "Special function."
6. Select "Learn neutral position of steering angle sensor."
7. Select and run "Initialization of steering angle sensor neutral position." (Reusable parts only)

Note Since the neutral position stored in the steering wheel sensor is no longer available,
"Initialization of steering angle sensor neutral position" is displayed.
Since a new steering wheel sensor has no neutral position, "Learn steering angle sensor

neutral position" is displayed.

8. Select and run "Learn steering angle sensor neutral position."
9. Exit "Steering angle sensor" menu, and then select "ABS/ASC/ASTC."
10. Select "Special function."
11. Select "Learn neutral position of steering angle sensor."
12. Select and run "Steering wheel sensor calibration."
13. Check whether the ASC-ECU-related diagnosis code is set.
14. Erase the diagnosis code.

Note Erase the diagnosis code C121A.

15. Turn the ignition key to the LOCK (OFF) position, and remove MUT-III from the vehicle.

MMMTC VER 1 MAC17 3 - 24

3. ACTIVE STABILITY CONTROL SYSTEM

<Brake Fluid Pressure Sensor Calibration>

Caution Before performing calibration, check that the brake fluid pressure sensor-related diagnosis
code is not set.

After the next operation has been completed, carry out the calibration to make ASC-ECU
learn the neutral position of the brake fluid pressure sensor.
Caution ◆ When the troubleshooting for code No. C123A is carried out
◆ Brake fluid pressure sensor replacement
◆ ASC-ECU replacement

Caution Always perform the calibration with the brake pedal released (stop lamp switch is turned
off).

1. Park the vehicle on a level surface.

2. Turn the ignition key to the LOCK (OFF) position, and connect MUT-III to the vehicle.
3. Turn the ignition switch to the ON position.

4. Select "ABS/ASC/ASTC."
5. Select "Special function."
6. Select "Sensor calibration."

7. Select "M/C pressure sensor calibration."
8. Turn the ignition key to the LOCK (OFF) position, and remove MUT-III from the vehicle.

<Steering Wheel Sensor/ Clock Spring/ Column Switch Assembly Installation>

1. Align the mating marks of the clock spring.

<Alignment of mating marks>
(1) Turn the clock spring clockwise fully.

(2) Turn the clock spring anti-clockwise approximately
three and 3/4 turns to align the mating marks.
(3) Install the clock spring to the column switch.

Be sure to remove the clock spring from the

column switch and centre the clock spring to

prevent the damage of steering wheel sensor.

Fig. 3-28 Caution If the centre of the clock spring is not correctly
aligned, the steering wheel may not be turned

fully or the cable inside the clock spring may

be broken, causing the SRS air bag to be inop-

erative or operated incorrectly.

2. Align three mating marks of the steering wheel sensor simulta-
neously as shown in the figure 3-27.
<Alignment of mating marks>
(1) Check the window for inspecting the neutral position of the
steering wheel sensor. If the mating marks cannot be seen from
the window, align the mating marks as shown in the figure.
(2) Install the steering wheel sensor to the column switch assem-
bly, maintaining the neutral position correctly.

A new steering wheel sensor has a pin for preventing the
Note rotation of (fixing) the steering wheel sensor. After in-

stalling the column switch assembly, remove this pin.

(3) Install the column switch assembly to the vehicle, maintaining
the neutral position correctly.

Fig. 3-29

3 - 25 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

(2) Data List Reference Table
The following items of ASC-ECU input data can be read using MUT-III.

Item Check item Check condition Normal condition
No. Perform a test run of the vehicle.
The speedometer display and the MUT-
1 FL wheel speed sensor III display almost agree with each other.
(During stop: approximately 0.7km/h)
2 FR wheel speed sensor

3 RL wheel speed sensor

4 RR wheel speed sensor

5 Power supply voltage System voltage (10 to 18 V ASC opera-
ble range)
7 Brake switch (input) The brake pedal is depressed.
The brake pedal is released. ON
8 Lateral G sensor Vehicle stopped (level)
(+: left turn, -: right turn) Running OFF
Vehicle stopped (level) 2WD
09 G sensor -0.11 to 0.11 G
(+: deceleration, 4WD
-: acceleration) -1 to 1 G
0 G*1 (fixed value)

-0.11 to 0.11 G
<Except vehicles with HSA>

Running 2WD -0.04 to 0.04 G
<Vehicles with HSA>
4WD 0 G*1 (fixed value)

10 Master cylinder pressure The brake pedal is depressed. -1 to 1 G
(+: pressure increase, Increases by the amount of the brake
-: pressure decrease) The brake pedal is released. pedal depression.

-3 to 3 bar

11 Steering angle Vehicle stopped (the steering -6 to 6 deg
(+: left turn, -: right turn) wheel is in the neutral position)
Nearly the same as the steering wheel
Running operation angle <-720 to 720 deg (ASC-
ECU normal detection value)>

Nearly the same as the steering wheel
operation angle <-850 to 850 deg
(Sensor normal value as a single unit)>

12 Yaw rate sensor Vehicle stopped (level) -3.6 to 3.6 deg/s
(+: left turn, -: right turn) Running -100 to 100 deg/s

14 Brake switch The brake pedal is depressed. ON
15 Emission test mode The brake pedal is released. OFF
Emission test mode: ON ON

Emission test mode: OFF OFF

26 Brake fluid pressure switch Brake fluid level is lower than the Low
"LOWER" marking.

Brake fluid level is higher than the Normal
"LOWER" marking.

28 ASC/TCL off switch When the ASC OFF switch is not ON
operated (when the ASC control is
available)

When the ASC OFF switch is oper- OFF
ated (pressed and held for 3 sec-
onds or more) (when the ASC con-
trol is prohibited)

When the ASC OFF switch is oper- ON
ated (pressed and held for 15 sec-
onds or more) (when the ASC OFF
control is prohibited by fail-safe
function)*2

MMMTC VER 1 MAC17 3 - 26

3. ACTIVE STABILITY CONTROL SYSTEM

Item Check item Check condition Normal condition
No.

45 SAS OK flag When the steering wheel sensor Comp
neutral point is learned Not Comp

When the steering wheel sensor
neutral point is not learned

When the steering wheel sensor is SAS fail

defective SAS fail & No Comp

65 Engine Speed When the accelerator pedal is de- The tachometer display and the MUT-III
66 Engine torque
67 APS pressed (engine started) display almost agree with each other.
68 Allow ESP torque request
70 Target gear When the selector or shift lever is Displays the engine torque.
71 Actual gear operated
72 Master cylinder Displays the accelerator pedal opening
angle.
pressure Offset Permitted

73 Lateral G sensor offset Displays the selector or shift lever posi-
tion.
86 Ignition switch
87 Ignition switch (input) The difference between the neutral -8 to 8 bar
88 Vehicle speed position that was input to the ASC-
91 Brake pressure sensor ECU before the master cylinder
pressure sensor calibration and the
96 G sensor offset neutral position after the calibra-
tion.

The difference between the neutral -0.15 to 0.15 G
position that was input to the ASC-
ECU before the G and yaw rate
sensor calibration and the neutral
position after the calibration.

Ignition switch: ON ON

Ignition switch: ON ON
Perform a test run of the vehicle.
The speedometer display and the MUT-
III display almost agree with each other.

The brake pedal is depressed. ON

The brake pedal is released. OFF
0 G*3 (fixed value)
The difference between 2WD
the neutral position that 4WD -0.15 to 0.15 G
was input to ASC-ECU <Except vehicles with HSA>
before the G and yaw rate
sensor calibration and the -0.08 to 0.08 G
neutral position after the <Vehicles with HSA>
calibration.

97 Yaw rate sensor offset The difference between the neutral -6.0 to 6.0 deg/s
position that was input to the ASC-
105 Power supply voltage ECU before the G and yaw rate
(input) sensor calibration and the neutral
position after the calibration.
120 Parking brake switch
(Input) System voltage (10 to 18 V ASC opera-
ble range)
128 A.S.C./TCL off switch
(input) When the parking brake lever is ON
pulled up:

When the parking brake lever is OFF
released:

The ASC OFF switch is pressed. ON

The ASC OFF switch is not operat- OFF
ed.

3 - 27 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

Item Check item Check condition Normal condition
No.
ASC-ECU is demanding the ESS
138 ESS request operation of ETACS-ECU. ON
OFF
ASC-ECU is not demanding the
ESS operation of ETACS-ECU.

Note *1: The G and yaw rate sensor does not detect longitudinal acceleration of a vehicle,
thus "0 G" is always set.
*2: When the ASC OFF switch is pressed and held for 15 seconds, the ASC system
returns to the ON status.
*3: The G and yaw rate sensor for 2WD vehicles does not detect longitudinal acceler-

ation of a vehicle, thus "0 G" is always set.
While ASC-ECU is disabled by the diagnostic function, the MUT-III displayed data is
different from the actual measurement.

MMMTC VER 1 MAC17 3 - 28

3. ACTIVE STABILITY CONTROL SYSTEM

(3) Actuator Test Table
Using MUT-III, the following actuators can be forcibly operated:

Note ABS and ASC are operated by ASC-ECU.
When ASC-ECU is disabled due to the fail-safe function, the actuator test cannot be per-
formed.

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, ABS warning lamp,
ASC operation display, and ASC OFF display illuminate until the ignition switch is turned to

ON again or the communication between MUT-III and ASC-ECU is terminated.

- Actuator Test Specifications -

Item Check item Driven component
No. Solenoid valve for the corresponding channel of the hydraulic unit and pump
motor (simplified inspection mode)
1 FL wheel ABS drive
Outputs the engine torque control signal (engine torque = 0 Nm) to the en-
2 FR wheel ABS drive gine ECU for three seconds.

3 RL wheel ABS drive

4 RR wheel ABS drive

5 FL wheel TCL drive

6 FR wheel TCL drive

7 RL wheel TCL drive

8 RR wheel TCL drive

9 Engine TCL drive

10 ESS test mode ASC-ECU requires an ESS operation of ETACS-ECU.

- Operation Pattern of Items 01 to 08 -

Fig. 3-30

3 - 29 MMMTC VER 1 MAC17

3. ACTIVE STABILITY CONTROL SYSTEM

5. KNOWLEDGE CHECK
Regarding the following sentences of Active Stability Control System, identify which ones are correct
or incorrect, and make the required correction to the wrong portion of the incorrect sentence.

(1) The ASC system integrates the transfer control (TCL) function and steering control function.

(2) When TCL detects the slip of the driving wheel (ex. during startup on low µ road), it automatically
applies the brakes to the slipping driving wheel.

(3) TCL reduces the engine coolant temperature and prevents the wheel spin when it determines that
the engine torque is too high for the road surface µ.

(4) Hill Start Assist (HSA) function has been adopted to hold and prevent the roll back of the vehicle
on a slope.

(5) The vehicle without TCL has a superior directional stability so that the required effort to maintain
the straight-ahead direction is much less than that of vehicle with TCL.

(6) The active traction control in M-ATSC automatically applies braking force to the freewheeling
drive wheels so that loss of driving power can be prevented.

(7) ASC-ECU controls the understeer or oversteer condition by creating the rolling moment in the ve-
hicle.

(8) The stability control manages the vehicle attitude by creating a yaw moment from altering the bal-
ance between the cornering force and each wheel’s brake mechanism.

(9) When vehicle tends to be under-steered, a yaw moment is created to restrain the under-steering
by increasing the rear-inside traction force.

(10) When vehicle tends to be oversteered, a yaw moment (a restorative moment) is created to re-
strain the oversteering by increasing the front-outside wheel braking force.

(11) Wheel speed sensor outputs the frequency signal in proportion to the rotation speed of engine to
ASC-ECU.

(12) G & yaw rate sensor Detects longitudinal and lateral acceleration of a vehicle, and outputs signal
to ASC-ECU via the CAN line.

(13) Brake fluid pressure sensor Integrated into the hydraulic unit, and outputs the signal for the
brake fluid pressure in the master cylinder to Engine-ECU.

(14) ASC operation display and lamp Informs the driver of the system status by flashing when the
system operates according to the signal from ASC-ECU.

(15) The G & yaw rate sensor is installed in the rear bumper, and detects the yaw rate, lateral and
longitudinal <except for 2WD> acceleration of the vehicle.

(16) The steering wheel sensor is attached to the column switch, and detects the rotational angle of
the steering wheel.

(17) Engine-ECU incorporates the ABS function, EBD function, stability control function, HSA func-
tion, and TCL function.

(18) When the next operation has been completed, carry out the calibration to make ASC-ECU learn
the neutral point of the steering wheel sensor, G and yaw rate sensor, and brake fluid pressure sen-
sor.

(19) The cut valve incorporated in the hydraulic unit is turned OFF when ASC-ECU performs the sta-
bility control and the traction control to apply brake pressure to the wheel cylinder.

(20) The suction valve incorporated in the hydraulic unit is turned ON when ASC-ECU performs the
stability control and the traction control to apply brake pressure to the wheel cylinder.

MMMTC VER 1 MAC17 3 - 30

SECTION IV

Electric Power Steering

CONTENTS

1. GENERAL ---------------------------------------------------------------------- 4-1
(1) Construction Diagram
(2) Specifications

2. SYSTEM OVERVIEW ------------------------------------------------------- 4-2/ 4-4
(1) Features
(2) Electrical Parts and Functions
(3) System configuration

3. SYSTEM OPERATION ----------------------------------------------------- 4-5
(1) Ignition Switch ON
(2) Steering Wheel Operation
(3) Fail-Safe Function

4. DIAGNOSTIC FUNCTION ------------------------------------------------- 4-6/ 4-7
(1) Electrical Power Steering Warning Display
(2) Freeze Frame Data
(3) Diagnostic Trouble Code

5. INSPECTION & SERVICE PROCEDURES --------------------------- 4-8/ 4-11
(1) Data List Reference Table
(2) Actuator Test Table

6. KNOWLEDGE CHECK ----------------------------------------------------- 4-12

4. ELECTRIC POWER STEERING

1. GENERAL

Electric power steering is a device to produce assistant force in order to reduce driver’s steering ef-
fort by adopting an electric motor (EPS motor). The drive current of the EPS motor is supplied from
the EPS-ECU, and the motor generates the assist torque in coping with the steering effort for either
rotating direction.

Steering effort Power supply Battery

Steering wheel Electric Power Vehicle speed, and etc.
Steering -ECU
Torque signal

Torque sensor EPS motor Calculation of
Reduction gear assist torque

Steering effort + Motor drive current
Assist torque

Pinion gear Rack gear
Fig. 4-1

Fig. 4-2 (1) Construction Diagram

Vehicle-speed sensitive electric power steer-
ing (whole range type) has been adopted.
This system allows a light steering force dur-
ing stationary steering maneuver or low
speed driving, and a moderate steering
force during medium or high speed driving.
The Electric Power Steering-ECU controls
the motor current according to the vehicle
speed and steering force of the steering
wheel. CAN* communication has been
adopted in order to communicate with other
ECUs for obtaining necessary information
related to this control, achieving wiring har-
ness saving and secure data communica-
tion.

(2) Specifications Specification
Permanent magnetic field coil type
Item
Type DC 12
79
Motor Rated voltage (V) Non-contact type
Rated current (Amp.)
LANCER-Ex (CY2A)
Torque sensor Type

Applicable model

4 - 1 MMMTC VER 1 MAC17

4. ELECTRIC POWER STEERING

2. SYSTEM OVERVIEW
(1) Features

In order to improve operational reliability, the dual-circuit system has been adopted for the torque
sensor. If any malfunction occurs in the electric power steering system, the fail-safe function of the
Electric Power Steering-ECU is activated, and the output current of the Electric Power Steering-ECU
applied to the motor is turned off. At the same time, the steering system enters manual mode, and
informs a driver of the system malfunction by illuminating the warning lamp on the combination me-
ter. The warning lamp illuminates when the following malfunctions occur;
◇ Open circuit in the electric power steering system wiring harness
◇ Poor connection

Fig. 4-3

(2) Electrical Parts and Functions

Sensor Parts Functions
Wheel speed sensor Sends the vehicle speed signal to the Electric Power Steering-ECU.
(ABS-ECU)
Detects a steering force, converts it into the voltage signal, and then
Torque sensor sends the signal to the Electric Power Steering-ECU.
Generates assist torque by the steering operation to the steering
Motor gear using the signals sent from the Electric Power Steering-ECU.
Detects the motor angle and sends the signal to the Electric Power
Actuator Motor angle sensor Steering-ECU.

Electric power steering Warns a driver of the system malfunction using the signal sent from

warning lamp the Electric Power Steering-ECU.

Controls the actuator (motor) based on the signal sent from sensor.

Electric Power Steering-ECU Controls the self-diagnostic function and fail-safe function.

Controls diagnostic function (communicate with MUT-III).

MMMTC VER 1 MAC17 4-2

4. ELECTRIC POWER STEERING

(3) System Configuration

Meter-ECU

ABS-ECU

Fig. 4-4

Note Dashed lines indicate CAN-bus lines.

<Steering Gear>
The torque sensor which detects an operated force of the steering wheel is installed in the steering
gear. When the steering wheel is turned, the steering force is detected by the torque sensor, and
the supply voltage signals (main and sub) from the torque sensor are input to the Electric Power
Steering-ECU.

Fig. 4-5 MMMTC VER 1 MAC17
4-3

4. ELECTRIC POWER STEERING

<Motor>
The motor is installed in the steering gear.
The steering motor is supplied with a con-
trol current sent from the Electric Power
Steering-ECU and generates the assist
torque to the steering gear according to the
steering operation.

Torsion bar Fig. 4-6 <Torque Sensor>
Multi magnet
Core (yoke) Input shaft Electric Power Steering-ECU can know the steering ef-
Hall IC fort by detecting the torsion angle of the torsion bar
through the torque sensor while steering. The hall IC
Flux ring element is used on the torque sensor to detect the tor-
Lower shaft sion amount. The output from the torque sensor is sent
to the Electric Power Steering-ECU, and the ECU utiliz-
es it to calculate the required assist torque by the motor.

Fig. 4-7 <Electric Power Steering-ECU>
Fig. 4-8 The Electric Power Steering-ECU is attached below
the glove box, which is integrated with an input inter-
face circuit, a microcomputer, an output drive circuit, a
fail-safe relay, and a motor line relay etc.
It is also integrated with a self-diagnostic function, and
illuminates the warning lamp and sets diagnosis code
to the diagnosis connector.

-CAN Communication-
The Electric Power Steering-ECU performs the data
transfer with other ECUs through CAN communication.

MMMTC VER 1 MAC17 4-4

4. ELECTRIC POWER STEERING
3. SYSTEM OPERATION
(1) Ignition Switch ON
Ignition supply voltage is applied to the Electric Power Steering-ECU, and the ECU enters standby
mode.
1. When the engine is started, the engine speed signal sent from the Engine-ECU is input to the

Electric Power Steering-ECU.
2. After starting the engine, the Electric Power Steering-ECU judges the engine status "ENGINE

SPEED ON" when the engine speed reaches 500 r/min then the power assist function is ready.

Fig. 4-9

(2) Steering Wheel Operation
1. When the steering wheel is operated, the torque sensor integrated into the gear box detects the

steering torque and outputs the torque sensor signal (main and sub), which varies with the
steering force, to the Electric Power Steering-ECU.
2. The Electric Power Steering-ECU outputs the current in proportion to the torque sensor signal
to the motor.
3. The motor outputs the rotational torque (assist torque) in proportion to the current intensity and
assists the power steering gear.

Fig. 4-10

(3) Fail-Safe Function Operation
If the Electric Power Steering-ECU detects any malfunction, it illuminates the warning lamp, deac-
tivates the electric power steering function. Then steering system can work as a manual steering.

4 - 5 MMMTC VER 1 MAC17

4. ELECTRIC POWER STEERING

4. DIAGNOSTIC FUNCTION
Electric Power Steering-ECU has the following functions for easier system checks using MUT-III.
◇ Diagnosis code set

◇ Service data output

<Diagnosis Code Set>
There are 28 DTC items. Since all the diagnostic results are recorded in volatile memory
(EEPROM*), they are retained in the memory even though the battery terminal is disconnected. (Max
8 DTCs)

Note *: EEPROM (Electrical Erasable & Programmable ROM), it is a special type of memory
that can be programmed or erased electrically.

(1) Electric Power Steering Warning Display
Check the electric power steering warning display as follows.

When the ignition switch is turned to the ON position,
the system check screen is displayed for about 4 sec-
onds. If there is no fault, information screen is displayed,
but if there is a fault in the electric power steering sys-
tem, the screen changes to warning display as shown in
the figure 4-11.

Fig. 4-11

(2) Freeze Frame Data
The freeze frame data can be checked by using MUT-III.

When the Electric Power Steering-ECU detects the trouble, it stores the diagnosis code. The ECU also
stores the ECU status of that time. By analyzing each data from MUT-III, the troubleshooting can be per-

formed more efficiently. The displayed items are as the table below.

No. Item Content 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
4 Accumulated minute (OFF)" after the past failure transition counts

Cumulative time for current malfunction of diagnosis code min

6 Torque sensor (main) Voltage of the main torque sensor when the diagnosis code is V
generated

7 Torque sensor (sub) Voltage of the sub torque sensor when the diagnosis code is V
generated

8 Torque sensor (power supply) Voltage of torque sensor power supply when the diagnosis V
code is generated

11 Relay voltage Voltage of power supply relay when the diagnosis code is gen- V
erated

12 Vehicle speed Vehicles speed when the diagnosis code is generated km/h

MMMTC VER 1 MAC17 4-6

4. ELECTRIC POWER STEERING

(3) Diagnostic Trouble Code

Caution During diagnosis, a diagnosis code associated with other system may be set when the ig-
nition switch is turned on with connector disconnected. On completion, confirm all systems
for diagnosis code. If diagnosis codes are set, erase them all.

If more than three minutes elapse after the ignition switch is turned ON without starting en-
gine, the Electric Power Steering-ECU may set diagnosis codes U0100 and U0121 as past

trouble.

Code No. Item

C1510 Torque sensor main

C1511 Torque sensor sub

C1512 Torque sensor main/sub voltage

C1513 Torque sensor power supply

C1514 Torque sensor power supply too low

C1520 Motor turning angle (input)

C1521 Motor turning angle (output)

C1522 Motor turning angle range

C1530 Motor FET driver

C1531 Motor current too low

C1532 Motor output current too large

C1533 Motor terminal initial voltage

C1534 Motor terminal monitor voltage

C1535 Motor output current

C1536 Motor terminal voltage abnormality (high voltage)

C1540 Power supply voltage abnormality (high voltage)

C1541 Power supply voltage abnormality (low voltage)

C1550 ECU internal error

C1560 Vehicle speed data (CAN) time-out

C1561 Engine revolution data (CAN) time-out

U0001 Bus off

U0100 Engine time-out error

U0121 ABS time-out error

U0141 ETACS time-out error

U0401 Engine revolution data input malfunction

U0415 Vehicle speed (CAN message) data input malfunction

U1415 Variant coding not implemented

U1417 Variant coding value invalid (includes faulty installation)

4 - 7 MMMTC VER 1 MAC17

4. ELECTRIC POWER STEERING

5. INSPECTION & SERVICE PROCEDURES

1. Data List Reference Table
The following data items can be read by the MUT-III from the Electric Power Steering-ECU.

No. Item Check condition Normal value
1 Torque sensor (main) Approximately 2.5 V
Start the engine. Centre position

Turn the steering wheel Steering wheel turned to right 2.5 - 4.7 V
with a vehicle station-
ary. Steering wheel turned to left 0.3 - 2.5 V

2 Torque sensor (sub) Start the engine. Centre position Approximately 2.5 V

Turn the steering wheel Steering wheel turned to right 2.5 - 0.3 V

with a vehicle station- Steering wheel turned to left 4.7 - 2.5 V
ary.

3 Torque sensor (power Start the engine. 4.7 - 5.3 V

supply)

4 Motor current Start the engine. Approximately 79
amps. or less

Turn the steering wheel to the left and right with a vehi- (When the steering
cle stationary. wheel is not operated,
approximately battery
voltage)

5 Motor current (target) Start the engine. Approximately 79
amps. or less

Turn the steering wheel to the left and right with a vehi- (When the steering
cle stationary. wheel is not operated,
approximately battery
voltage)

7 Engine speed Start the engine. Tachometer displayed
8 Vehicle speed Turn the steering wheel to the left and right with a vehi- value and MUT-III dis-
11 Ignition switch cle stationary. played value agree
with each other.
Start the engine.
Turn the steering wheel to the left and right with a vehi- Speed meter displayed
cle stationary. value and MUT-III dis-
played value agree
Ignition switch: LOCK (OFF) with each other.

CAN communication
error

Ignition switch: ON ON

16 Motor current (unlimited Start the engine. Approximately 79

target) Turn the steering wheel to the left and right with a vehi- amps. or less

cle stationary.

17 Motor electric angle Start the engine. 0 - 360 deg

Turn the steering wheel to the left and right with a vehi- Motor angle
cle stationary.

18 Motor speed Start the engine. Rated value: 1130 rpm

Turn the steering wheel to the left and right with a vehi- (neutral: 0 rpm)

cle stationary.

19 Motor voltage Start the engine. Voltage between the
motor terminals: rated
value 12 V)

MMMTC VER 1 MAC17 4-8

4. ELECTRIC POWER STEERING

(Continued from previous page)

No. Item Check condition Normal value
19 Motor voltage Start the engine. Voltage between the
motor terminals: rated
22 Power relay voltage Ignition switch: ON value 12 V)

23 Ignition voltage Start the engine. Initialized
24 Power relay Ignition switch: ON
Battery voltage
25 Motor relay Ignition switch: ON
Start the engine Battery voltage
A11 Odometer :rec.A1 Ignition switch: ON
OFF
A12 Motor current Start the engine.
(target) :rec.A1 Assist limitation does not occur. ON
Assist limitation occurs. OFF
Assist limitation does not occur.
Assist limitation occurs. ON

A13 Motor current (unlimited Assist limitation does not occur. Memorized value *1

target) :rec.A1 Assist limitation occurs. Odometer value

A14 Motor current :rec.A1 Assist limitation does not occur. Memorized value *1

A15 Vehicle speed :rec.A1 Assist limitation occurs. Current value: 79
Assist limitation does not occur. amps. or less
A21 Odometer :rec.A2 Assist limitation occurs.
Assist limitation does not occur. Memorized value *1
A22 Motor current Assist limitation occurs.
(target) :rec.A2 Assist limitation does not occur. Current value (before
Assist limitation occurs. the assist limitation)

A23 Motor current (unlimited Assist limitation does not occur. Memorized value *1

target) :rec.A2 Assist limitation occurs. Actual current value
Memorized value *1
A24 Motor current :rec.A2 Assist limitation does not occur. Speedometer value
Memorized value *1
A25 Vehicle speed :rec.A2 Assist limitation occurs. Odometer value
Assist limitation does not occur. Memorized value *1
A31 Odometer :rec.A3 Assist limitation occurs. Current value: 79
Assist limitation does not occur. amps. or less
A32 Motor current Assist limitation occurs.
(target) :rec.A3 Assist limitation does not occur. Memorized value *1
Assist limitation occurs.
Current value (before
A33 Motor current (unlimited Assist limitation does not occur. the assist limitation)

target) :rec.A3 Assist limitation occurs. Memorized value *1

A34 Motor current :rec.A3 Assist limitation does not occur. Actual current value
Assist limitation occurs. Memorized value *1
A35 Vehicle speed :rec.A3 Assist limitation does not occur. Speedometer value
Assist limitation occurs. Memorized value *1
A41 Odometer :rec.A4 Assist limitation does not occur. Odometer value
Assist limitation occurs. Memorized value *1
A42 Motor current Assist limitation does not occur. Current value: 79
(target) :rec.A4 Assist limitation occurs. amps. or less

Memorized value *1
Current value (before
the assist limitation)

Memorized value *1
Actual current value
Memorized value *1
Speedometer value
Memorized value *1
Odometer value
Memorized value *1
Current value: 79
amps. or less

4 - 9 MMMTC VER 1 MAC17

4. ELECTRIC POWER STEERING

(Continued from previous page)

No. Item Check condition Normal value
Memorized value *1
A43 Motor current (unlimited Assist limitation does not occur.
Current value (before
target) :rec.A4 Assist limitation occurs. the assist limitation)

A44 Motor current :rec.A4 Assist limitation does not occur. Memorized value *1

A45 Vehicle speed :rec.A4 Assist limitation occurs. Actual current value
Assist limitation does not occur. Memorized value *1
A51 Odometer :rec.A5
A52 Motor current Assist limitation occurs. Speedometer value

(target) :rec.A5 Assist limitation does not occur. Memorized value *1
Assist limitation occurs. Odometer value
Assist limitation does not occur. Memorized value *1
Assist limitation occurs. Current value: 79
amps. or less
A53 Motor current (unlimited Assist limitation does not occur.
Memorized value *1
target) :rec.A5 Assist limitation occurs. Current value (before
the assist limitation)
A54 Motor current :rec.A5 Assist limitation does not occur.
A55 Vehicle speed :rec.A5 Assist limitation occurs. Memorized value *1
B11 Odometer :rec.V1 Assist limitation does not occur. Actual current value
Assist limitation occurs. Memorized value *1
Battery voltage down does not occur. Speedometer value
Memorized value *2
Battery voltage down occurs.
Odometer value when
B12 Power relay voltage :rec Battery voltage down does not occur. battery voltage down
V1 Battery voltage down occurs. occurs.

B13 Vehicle speed :rec.V1 Battery voltage down does not occur. Memorized value *2

Battery voltage down occurs. Relay contact voltage

B21 Odometer :rec.V2 Battery voltage down does not occur. Memorized value *2
Battery voltage down occurs.
Vehicle speed when
B22 Power relay voltage :rec Battery voltage down does not occur. battery voltage down
V2 Battery voltage down occurs. occurs.

B23 Vehicle speed :rec.V2 Battery voltage down does not occur. Memorized value *2

Battery voltage down occurs. Odometer value when
battery voltage down
B31 Odometer :rec.V3 Battery voltage down does not occur. occurs.
Battery voltage down occurs.
Memorized value *2
B32 Power relay voltage :rec Battery voltage down does not occur.
V3 Battery voltage down occurs. Relay contact voltage

B33 Vehicle speed :rec.V3 Battery voltage down does not occur. Memorized value *2

Battery voltage down occurs. Vehicle speed when
battery voltage down
occurs.

Memorized value *2

Odometer value when
battery voltage down
occurs.

Memorized value *2

Relay contact voltage

Memorized value *2

Vehicle speed when
battery voltage down
occurs.

Note When the diagnosis system stops the Electric Power Steering-ECU, the MUT-III display da-
ta will be un-reliable.

MMMTC VER 1 MAC17 4 - 10

4. ELECTRIC POWER STEERING

(Continued from previous page)

No. Item Check condition Normal value
B41 Odometer :rec.V4 Battery voltage down does not occur. Memorized value *2

Battery voltage down occurs. Odometer value when battery
voltage down occurs.
B42 Power relay voltage :rec V4 Battery voltage down does not occur.
B43 Vehicle speed :rec.V4 Battery voltage down occurs. Memorized value *2
Battery voltage down does not occur.
Battery voltage down occurs. Relay contact voltage

B51 Odometer :rec.V5 Battery voltage down does not occur. Memorized value *2
Battery voltage down occurs.
Vehicle speed when battery
B52 Power relay voltage :rec V5 Battery voltage down does not occur. voltage down occurs.
B53 Vehicle speed :rec.V5 Battery voltage down occurs.
Battery voltage down does not occur. Memorized value *2
Battery voltage down occurs.
Odometer value when battery
voltage down occurs.

Memorized value *2

Relay contact voltage

Memorized value *2

Vehicle speed when battery
voltage down occurs.

Note: Memorized value*1
This is a value of the corresponding item that is recorded at the moment when the Power Steering-
ECU terminates the power steering assist operation in order to suppress the circuit temperature rise.
There are 5 memory spaces from A1 to A5, each space A stores the data of Odometer, Motor current
(target), Motor current (unlimited target), Motor current and Vehicle speed. Data update is carried out
automatically, and shows the latest 5 cases.

If the vehicle is driven under heavy load (Ex. consecutively turning the steering to full lock or severe
cornering), the electric power steering motor drive circuit will become hot. In this case, the electric
power steering system will limit assist operation by decreasing the motor current to avoid damage. In
this case, the steering will become heavy, but the electric power steering warning lamp does not illu-
minate. If the circuit temperature reduces after a while, the assist operation will return to the normal
level.

Note: Memorized value*2
This is a value of the corresponding item that is recorded at the moment when the Power Steering-
ECU terminates the power steering assist operation due to low battery voltage detection.
There are 5 memory spaces from V1 to V5, each space V stores the data of Odometer, Power relay
voltage and Vehicle speed. Data update is carried out automatically, and shows the latest 5 cases.

(2) Actuator Test Table

The MUT-III activates the following actuators for testing, but the Electric Power Steering-ECU runs
down, actuator testing cannot be carried out. Actuator testing is only possible when the vehicle is sta-
tionary.

No. Check item Driven component

10 Input vehicle speed Steering assist control

4 - 11 MMMTC VER 1 MAC17

4. ELECTRIC POWER STEERING

6. KNOWLEDGE CHECK
Regarding the following sentences of Electric Power Steering, identify which ones are correct or in-
correct, and make the required correction to the wrong portion of the incorrect sentence.

(1) LIN communication has been adopted in order to communicate with other ECUs for obtaining
necessary information related to this control, achieving wiring harness saving and secure data com-
munication.

(2) In order to improve operational reliability, the dual-circuit system has been adopted for the torque
sensor.

(3) If any malfunction occurs in the electric power steering system, the fail-safe function of the Elec-
tric Power Steering-ECU is activated, and the output current of the Electric Power Steering-ECU ap-
plied to the motor is not turned off.

(4) Wheel speed sensor sends the vehicle speed signal to the Electric Power Steering-ECU.

(5) Torque sensor detects a traction force, converts it into the voltage signal, and then sends the sig-
nal to the Electric Power Steering-ECU.

(6) Motor Generates assist torque by the steering operation to the steering gear using the signals
sent from the Electric Power Steering-ECU.

(7) Motor angle sensor detects the motor rotation speed and sends the signal to the Electric Power
Steering-ECU.

(8) Electric power steering warning lamp warns a driver of the system malfunction using the signal
sent from the Electric Power Steering-ECU.

(9) Electric Power Steering-ECU controls the actuator (motor) based on the signal sent from actuator.

(10) Electric Power Steering-ECU Controls the self-diagnostic function and fail-safe function.

(11) Electric Power Steering-ECU Controls diagnostic function by communicating with your mobile
phone.

(12) The torque sensor which detects an operated force of the steering wheel is installed in the steer-
ing gear.

(13) The motor is installed in the steering gear. The steering motor is supplied with a control current
sent from the Engine-ECU and generates the assist torque to the steering gear according to the
steering operation.

(14) The Electric Power Steering-ECU is integrated with an input interface circuit, a microcomputer,
an output drive circuit, a fail-safe relay, and a motor line relay etc.

(15) The Electric Power Steering-ECU performs the data transfer with other ECUs through LIN com-
munication.

(16) After starting the engine, the Electric Power Steering-ECU judges the engine status "ENGINE
SPEED ON" when the engine speed reaches 500 r/min then the power assist function is ready.

(17) When the steering wheel is operated, the torque sensor integrated into the wheel detects the
steering torque and outputs the torque sensor signal (main and sub), which varies with the steering
force, to the Electric Power Steering-ECU.

(18) The Electric Power Steering-ECU outputs the current in proportion to the torque sensor signal to
the motor.

(19) If the Electric Power Steering-ECU detects any malfunction, it illuminates the ABS warning lamp,
deactivates the electric power steering function. Then steering system can work as a manual steer-
ing.

(20) Since all the diagnostic results are recorded in volatile memory, they are retained in the memory
even though the battery terminal is disconnected.

MMMTC VER 1 MAC17 4 - 12

SECTION V

Supplemental Restraint
System

CONTENTS

1. GENERAL ---------------------------------------------------------------------- 5-1/ 5-3
(1) Features
(2) Construction Diagram
(3) SRS System Circuit Diagram

2. SYSTEM OPERATION ----------------------------------------------------- 5-4
(1) Dual Stage Airbags/ Knee Airbag/ Seat Belt Pre-tentioner
(2) Side and Curtain Airbags

3. SYSTEM CONSTRUCTION ----------------------------------------------- 5-5/ 5-10
(1) Driver’s Airbag Module
(2) Front Passenger’s Airbag Module
(3) Knee Airbag Module
(4) Side-Airbag Module
(5) Curtain Airbag Module
(6) Clock spring
(7) Front Impact Sensor
(8) Side Impact Sensor
(9) Seat Belt Pre-tentioner
(10) SRS-ECU
(11) SRS Airbag Special Connector

4. DIAGNOSIS FUNCTION --------------------------------------------------- 5-11/ 5-12
(1) Diagnosis Code Set
(2) Data List Output
(3) Actuator test

5. INSPECTION & SERVICE PROCEDURES --------------------------- 5-13/ 5-15
(1) Service Precautions
(2) On Post-Collision
(3) Clock Spring Installation
(4) Freeze Frame Data
(5) Data List Reference Table
(6) Actuator Test Table

6. KNOWLEDGE CHECK ----------------------------------------------------- 5-16

5. SUPPLEMENTAL RESTRAINT SYSTEM

1. GENERAL
The supplemental Restraint System (SRS) is designed to supplement the seat belt to reduce the risk
or severity of injury to the occupants in the cabin by activating and deploying airbags in certain frontal
or lateral collisions.
The SRS consists of the following main parts; impact sensors, clock spring (connecting harness be-
tween chassis electrical wiring harness and driver’s airbag), airbag module and SRS-ECU.
In the event of a collision, the signal from the impact sensor which has detected the collision goes
through the SRS-ECU , and the ECU ignites the inflator built-in the airbag module, then the generat-
ed gas instantly inflates the airbag.
The airbag deployment steps are typically illustrated in the figure 5-1. Since the impact which re-
quires the airbag to deploy is detected, approx. 40 milliseconds elapses before the airbag to be fully
inflated, thereafter airbag absorbs the occupant body moving and shrinks.

Fig. 5-1

1. Features
The supplement restraint system employed on LANCER-EX has the following features.
◇ The SRS airbag is a system that is effective with the seat belt fastened, and it is designed as a

supplemental system of the seat belt.
◇ The dual stage airbags have been adopted to the driver’s and the front passenger’s sides. When

a frontal impact exceeds the threshold upon a frontal collision, or depending on the severity of
impact, the airbag inflates the cushion airbag in two stages, improving the protection for the front
seat passengers.
◇ The driver’s knee airbag is activated when an impact exceeds the threshold upon a frontal colli-

sion, and the cushion airbag is instantaneously inflated for better protection of the driver.
◇ The side-airbag is activated when an impact exceeds the threshold upon a side collision, and the

cushion airbag is instantaneously inflated to protect the chest area of the front seat passengers.
◇ The curtain airbag is activated simultaneously with the side-airbag upon a side collision to protect

the heads of the front seat and second seat passengers.
◇ For the inflator, the gas which is harmless to the human body has been adopted.

◇ The seat belt pre-tensioner is activated simultaneously with the deployment of driver’s and the

front passenger’s airbags in case of a frontal collision. Seat belts are pulled in to eliminate the
slack upon a collision, thus improving the initial occupant restraint, and reducing the travel dis-
tance of the occupants.

Caution Do not disassemble the SRS airbag components or seat belt with pre-tensioner. Also, do
not apply any impact on them.

5 - 1 Pub. No. PTAE1310

5. SUPPLEMENTAL RESTRAINT SYSTEM
2. Construction Diagram

Pub. No. PTAE1310 Fig. 5-2
5-2

5. SUPPLEMENTAL RESTRAINT SYSTEM
3. SRS System Circuit Diagram

(1st squib)
(2nd squib)
(1st squib)
(2nd squib)

(CAN_H)
(CAN_L)

Fig. 5-3 Pub. No. PTAE1310
5-3