Mitsubishi Lancer Evolution X. Manual — part 135

GENERAL INFORMATION

TSB Revision

ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-5

MAIN COMPONENTS AND FUNCTIONS

Parts name

No. Functional description

Sensor

Wheel speed sensor

1

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

Magnetic encoder for
wheel speed detection

2

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 sensor outputs frequency pulse signal in
proportion to each wheel speed.

Stoplight switch

3

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

G and yaw rate sensor

4

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

Steering wheel sensor

5

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

ASC OFF switch

6

Outputs the ASC ON/OFF signal to ASC-ECU.

Master cylinder pressure
sensor

7

Integrated into the hydraulic unit, converts the signal of
brake fluid pressure in master cylinder to the voltage
value, then outputs the value to ASC-ECU.

Wheel cylinder pressure
sensor

8

Integrated into the hydraulic unit, converts the signal of
brake fluid pressure in wheel cylinder of each wheel to
the voltage value, then outputs the value to ASC-ECU.

Actuator

Hydraulic unit

9

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

ABS warning light

10

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

ABS warning display

11

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

Brake warning light

12

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

Brake warning display

13

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

ASC operation display
and light

14

According to the signal from ASC-ECU, flashes when
the system is active to inform the driver of the status.

ASC warning display and
light

15

The TCL function and skid control function use the
same display. According to the signal from ASC-ECU,
the display is illuminated to inform the driver that the
system is abnormal.

ASC OFF display

16

Informs the driver of the ASC system shutdown by
illuminating according to the signal from ASC-ECU.

SERVICE SPECIFICATIONS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-6

NOTE:

*

: Only for vehicles with TC-SST

SERVICE SPECIFICATIONS

M1355008200108

DIAGNOSIS

INTRODUCTION TO ASC DIAGNOSIS

M1355000800054

The active stability control system (ASC) operates
differently from conventional brake systems. These
differences include sounds, sensations, and vehicle
performance that owners and service technicians
who are not familiar with ASC may not be used to.

Some operational characteristics may seem to be
malfunctions, but they are simply signs of normal
ASC operation. When diagnosing the ASC system,
keep these operational characteristics in mind.
Inform the owner of the kind of performance charac-
teristics to expect from an ASC-equipped vehicle.

ASC DIAGNOSTIC TROUBLE CODE
DETECTION CONDITIONS

ASC diagnostic trouble codes (ASC DTCs) are set
under different conditions, depending on the mal-
function detected. Most ASC DTCs will only be set
during vehicle operation. Some ASC DTCs will also
be set during the ASC self-check immediately after
the engine is started.

When you check if an ASC DTC will be displayed
again after the DTC has been erased, you should
duplicate the ASC DTC set conditions. Depending on
the detection timing and set conditions for the spe-
cific ASC DTC, you must either drive the vehicle or
turn the engine off and restart it. To set the proper
conditions for that DTC again, refer to "ASC DTC
SET CONDITIONS" for each ASC DTC that you are
trying to reset.

ASC DIAGNOSTIC TROUBLESHOOTING STRATEGY

M1355000900147

Use these steps to plan your diagnostic strategy. If
you follow them carefully, you will be sure that you
have exhausted most of the possible ways to find an
ASC fault.

1. Gather information about the problem from the

customer.

2. Verify that the condition described by the

customer exists.

3. Check the vehicle for any ASC DTC.

Data link connector

17

Outputs the diagnostic trouble code and establishes
the communication with the scan tool.

Engine Control Module (ECM)

18

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

TC-SST ECU

*

19

*

Outputs the shift position to ASC-ECU.

AWC ECU

20

Outputs the drive status and brake fluid pressure
request to ASC-ECU.

ASC-ECU

21

Controls the actuators (described above) based on the
signals coming from each sensors.
Controls the self-diagnostic functions and fail-safe
functions.
Controls diagnostic function (Compatible with scan
tool).

Parts name

No. Functional description

Item

Standard value

Wheel speed sensor current mA

5.9 − 8.4 or 11.8 − 16.8

Wheel speed sensor insulation resistance MΩ

5 or more

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-7

4. If you cannot verify the condition and there are no

ASC DTCs, the malfunction is intermittent. Refer
to GROUP 00, How to use
Troubleshooting/Inspection Service Points − How

to Cope with Intermittent Malfunctions

P.00-15

.

5. If you can verify the condition but there are no

ASC DTCs, or the system cannot communicate
with the scan tool, check that the basic brake
system is operating properly.

• If the basic brake system is not operating prop-

erly, refer to the GROUP 35A, Basic Brake Sys-
tem Diagnostic troubleshooting strategy

P.35A-4

.

• If the basic brake system is operating properly,

refer to

P.35C-232

.

6. If there is an ASC DTC, record the number of the

DTC, then erase the DTC from the memory using
the scan tool.

7. Recreate the ASC DTC set conditions to see if the

same ASC DTC will set again.

• If the same ASC DTC sets again, perform the

diagnostic procedures for the DTC. Refer to

P.35C-22

.

• If you cannot get the same ASC DTC to set

again, the malfunction is intermittent. Refer to
GROUP 00, How to use Troubleshooting/Inspec-
tion Service Points − How to Cope with Intermit-

tent Malfunctions

P.00-15

.

PRECAUTIONS FOR DIAGNOSIS

M1355009500113

1. ASC controls the brake pressure by the assistance of ECU.

The symptoms described in the table below may occur
during the normal ASC operation. However, they do not
indicate any sign of malfunction.

2. On snowy or gravel roads, a vehicle with ABS sometimes

requires a longer braking distance compared to the one
without ABS. Considering this characteristics, advise the
customer to drive the vehicle safely at lower speed and not
to place too much confidence on the ABS system when
driving on such roads.

3. The detection conditions of diagnostic trouble code differ

with each diagnostic trouble code. When the trouble
symptoms are rechecked, conditions described in the
description for the diagnostic trouble code procedures must
be satisfied.

Symptoms

Description of symptoms

• When ASC operates, the operating noise is generated from

the motor integrated in the hydraulic unit. (Screech)

• Noise is generated from the brake pedal together with the

vibration. (Boom, boom)

• When ASC operates, the system repeats the activation and

deactivation. At this time, the noise is generated from the
chassis components. (Clunk: Suspension; Squeak: Tire)

These noises are generated when the
system and brake pedal operate
normally, and they do not indicate any
sign of malfunction.

• A slight shock is felt occasionally when the brake pedal is

depressed lightly during the low speed driving.

• Small clicking noise is heard occasionally from the engine

compartment.

This noise is generated when the system
operation check <startup check
performed when the vehicle speed is at
few km/h (mile)> is performed, and it
does not indicate any malfunction.

DIAGNOSIS

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ACTIVE STABILITY CONTROL SYSTEM (ASC)

35C-8

ABS WARNING LIGHT, ASC
WARNING/OPERATION LIGHT AND BRAKE
WARNING LIGHT CHECK

M1352012001071

Check that ABS and brake warning light, ASC warning/opera-
tion light illuminate as follows.
NOTE: The brake warning light is used as the warning lights for
the parking brake, brake fluid level, and EBD control.
1. When the ignition switch is turned to the ON position, ABS

and brake warning light, ASC warning/operation light
illuminate.

2. The ABS and brake warning light, ASC warning/operation

light illuminate for three seconds

*1

and then turn OFF

*2

.

3. Other than the above, the system may have a malfunction.

Check the diagnostic trouble code.

NOTE:

.

•

*1

: The ABS warning light may stay ON until the vehicle

speed reaches 10 km/h. As far as ABS-ECU stores any
diagnostic trouble code related to the wheel speed sensor
malfunction or the motor malfunction as past trouble,
ABS-ECU continues illuminating the ABS warning light until
it verifies that the malfunction for that code is resolved (star-
tup check).

•

*2

: The brake warning light does not turn OFF when the

parking brake is applied or the brake fluid level is lowered.

DIAGNOSTIC FUNCTION

M1355001000545

ASC-ECU has the following functions for easier sys-
tem checks. All the following items can be diagnosed
using the scan tool.

• Diagnostic trouble code set (Refer to

P.35C-22

.)

• Service data output (Refer to

P.35C-276

.)

• Actuator test (Refer to

P.35C-278

.)

• Freeze frame data output (Refer to

P.35C-8

).

All the above items can be diagnosed using scan
tool.

CHECK OF FREEZE FRAME DATA

The freeze frame data can be checked by using the
scan tool.

.

When detecting fault and storing the DTC, the ECU
connected to CAN bus line obtains the data before
the determination of the DTC and the data when the
DTC is determined, and then stores the ECU status
of that time. By analyzing each data from scan tool,
the troubleshooting can be performed more effi-
ciently. The displayed items are as the table below.

AC901746AC

ABS warning light

ABS warning
light, Brake
warning light,
ASC warning/
operation light

Ignition switch

Illuminated

Approximately 3s

ON
ACC,
LOCK

START

Not
illuminated

ASC warning/
operation light

Brake warning light
<Vehicles for CANADA>

Brake warning light
<Vehicles for USA>