Mitsubishi Evolution X. Manual - part 749

GENERAL INFORMATION

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-3

CONSTRUCTION DIAGRAM

.

AC708742

CHECK

SERVICE
         REQUIRED

SERVICE
         REQUIRED

10

12

13

11

15

14

17

5

3

19

AB

1

1

2

2

4

20

16

7, 8, 9, 22

6

18

21

GENERAL INFORMATION

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-4

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.

GENERAL INFORMATION

TSB Revision

ACTIVE SKID CONTROL SYSTEM (ASC)

35C-5

NOTE: 

.

•

*1

: For information on AYC (Active Yaw Control), 

refer to technical information manual.

•

*2

: Only for vehicles with TC-SST

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 warning light according to 
the signal from ASC-ECU.

ASC operation display

14

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

ASC warning display

15

The TCL function and ASC 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 light

16

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

ASC OFF display

17

Using the signal from ASC-ECU, the display is 
illuminated to inform the driver that the ASC OFF 
switch is pressed and held for 3 seconds, and that the 
ASC and AYC

*1

 brake control is prohibited.

Data link connector

18

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

Engine ECU

19

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

TC-SST ECU

*2

20

*2

Outputs the shift position to ASC-ECU.

S-AWC ECU

21

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

ASC-ECU

22

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

SERVICE SPECIFICATIONS

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ACTIVE SKID CONTROL SYSTEM (ASC)

35C-6

SERVICE SPECIFICATIONS

M1355008200108

DIAGNOSIS

INTRODUCTION TO ASC DIAGNOSIS

M1355000800054

The active skid control system (ASC) operates differ-
ently from conventional brake systems. These differ-
ences 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.
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-219

.

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-20

.

• 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

.

Item

Standard value

Wheel speed sensor current  mA

5.9 

− 8.4 or 11.8 − 16.8

Wheel speed sensor insulation resistance  M

Ω

5 or more