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Mitsubishi Lancer Evolution 7. Manual - part 322

ABS <4WD> -

On-vehicle Service

35B-27

4. Rotate the wheel to be measured at approximately 1/2 - 1

rotation per second, and check the output voltage using a

circuit tester or an oscilloscope.

Wheel speed

sensor

Front

left

Front

right

Rear

left

Rear

right

Terminal No.

Output voltage

When measuring with a circuit tester:

42 mV or more

When measuring with an oscilloscope:

120 mV p-p or more

5. The followings are suspected if the output voltage is lower

than the value described above. Check the wheel speed

sensor, and replace if necessary.
D

Too large clearance between the pole piece of the

wheel speed sensor and ABS rotor

Faulty wheel speed sensor

Inspecting Waveforms With An Oscilloscope
Use the following method to observe the output voltage

waveform from each wheel speed sensor with an oscilloscope.
D

Start the engine, and rotate the front wheels by engaging

1st gear. Turn the rear wheels manually so that they

rotate at a constant speed.

NOTE

1. The waveform measurements can also be taken while

the vehicle is actually moving.

2. The output voltage will be small when the wheel speed

is low, and similarly it will be large when the wheel speed

is high.

Points In Waveform Measurement

Symptom

Probable causes

Remedy

Too small or zero waveform

amplitude

Faulty wheel speed sensor

Replace sensor

Waveform amplitude fluctuates

excessively (this is no problem if

Axle hub eccentric or with large runout

Replace hub

excessively (this is no problem if

the minimum amplitude is 100 mV

or more)

Faulty ABS-ECU earth

Repair

When turning by hand

When idling (5 - 6 km/h), 1st gear

10.0 ms/DIV 1 V/DIV

ABS <4WD> -

On-vehicle Service

35B-28

Symptom

Remedy

Probable causes

Noisy or disturbed waveform

Open circuit in sensor

Replace sensor

Open circuit in harness

Correct harness

Incorrectly mounted wheel speed sensor

Mount correctly

ABS rotor with missing or damaged teeth

Replace ABS rotor

Caution

Because the wheel speed sensor cables move together with the front and rear suspension, they

vibrate greatly when driving over poor road surfaces. As a result, the sensor harnesses should also

be shaken when monitoring of output waveforms of the wheel speed sensors in order to simulate

conditions such as driving over poor road surfaces.

HYDRAULIC UNIT CHECK

1. Jack up the vehicle and support the vehicle with rigid racks placed at the specified jack-up points

or place the wheels which are checked on the rollers of the braking force tester.
Caution

(1) The roller of the braking force tester and the tyre should be dry during testing.

(2) When testing the front brakes, apply the parking brake, and when testing the rear brakes,

stop the front wheels by chocking them.

2. Turn the ignition key to the “LOCK” (OFF) position and set the MUT-II.

Caution

Turn the ignition key to the “LOCK” (OFF) position before connecting or disconnecting the

MUT-II.

3. After checking that the shift lever is in neutral, start the engine.

4. Use the MUT-II to force-drive the actuator.

NOTE

(1) During the actuator test, the ABS warning lamp will illuminate and the anti-skid control will be

cancelled.

(2) When the ABS has been interrupted by the fail-safe function, the MUT-II actuator testing cannot

be carried out.

5. Turn the wheel by hand and check the change in braking force when the brake pedal is depressed.

When using the braking force tester, depress the brake pedal until the braking force is at the following

values, and check that the braking force decreases when the actuator is force-driven.

Front wheel

785 - 981 N

Rear wheel

588 - 784 N

ABS <4WD> -

On-vehicle Service

35B-29

The result should be as shown in the following diagram.

Approx. 0.05 seconds

Pedal operation

Depressed

Released

Solenoid valve

position

Increase in pressure

Steady pressure

Reduction in pressure

Checking the

brake force

Lock

Drag force when the pedal is free

MUT-II actuator test

(Item No. 01, 02, 03, 04) start

2 seconds

1 seconds

6. If the result of inspection is abnormal, correct according to the following “Diagnosis Table.”
Diagnosis Table

No.

MUT-II

display

Operation

Judgement

Probable

cause

Remedy

display

Normal

Abnormal

cause

FR VALVE

(1) Depress the brake

pedal to lock wheel.

(2) Using

the

MUT-II,

select the wheel to be

checked and force the

Brake force

released for 3

seconds after

locking.

Wheel does

not lock when

brake pedal

is depressed.

Clogged

brake line

other than

hydraulic unit

Check and

clean brake

line.

FL VALVE

checked and force the

actuator to operate.

(3) Check the brake force

for the selected wheel

using a brake force

t t

t ti

Clogged

hydraulic

circuit in

hydraulic unit

Replace

hydraulic unit

assembly.

RR VALVE

tester or by rotating the

wheel by hand.

Brake force is

not released.

Incorrect

hydraulic unit

brake tube

connection

Connect

correctly.

RL VALVE

Hydraulic unit

solenoid

valve not

functioning

correctly

Replace

hydraulic unit

assembly.

7. After checking, turn the ignition switch to the “LOCK” (OFF) position and then disconnect the MUT-II.

REMEDY FOR A FLAT BATTERY

When booster cables are used to start the engine when the

battery is completely flat and then the vehicle is immediately

driven without waiting for the battery to recharge itself to

some extent, the engine may misfire, and driving might not

be possible. This happens because ABS consumes a great

amount of current for its self-check function. If this happens,

recharge the battery fully.
Caution

The vehicle posture will be unstable during braking, so

do not drive the vehicle with the ABS-ECU connector

disconnected or with the ABS not operating for any other

reason.

ABS <4WD> -

Hydraulic Unit and ABS-ECU

35B-30

HYDRAULIC UNIT AND ABS-ECU

REMOVAL AND INSTALLATION

<L.H. drive vehicles>

Pre-removal Operation
D

Strut Tower Bar Removal (Refer to GROUP 42.)

Brake Fluid Draining

Post-installation Operation
D

Brake Fluid Supplying and Brake Line Bleeding

(Refer to GROUP 35A - On-vehicle Service.)

Hydraulic Unit Check (Refer to P.35B-28.)

Strut Tower Bar Installation (Refer to GROUP 42.)

15 ± 2 N·m

25 ± 6 N·m

Removal steps

1. Harness connector

AA 2. Brake pipe connection

3. Hydraulic unit and ABS-ECU

4. Hydraulic unit bracket assembly

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