Isuzu N-Series. Service manual — part 242

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-33

H-5

H-6, H-7, H-8

R-6

No.

Connector Face

006-005

3

6

1

4

2

5

1

2

3

7

8

9

13

14 15

19

20 21

25

26 27

31

32 33

34

35

36

37

4

5

6

10

11 12

16

17 18

22

23 24

28

29 30

38

39 40

6

5

4

12

11 10

18

17 16

24

23 22

30

29 28

40

39 38

3

2

1

9

8

7

15

14 13

21

20 19

27

26 25

33

32 31

34

35

36

37

N8A5488E

1

2

1

2

1 2 3 4

5 6 7 8

9 10 11 12 13

14 15 16 17 18

2

1

2

1

4 3 2 1

8 7 6 5

13 12 11 10 9

18 17 16 15 14

H - 6

H - 7

H - 8

N8A5489E

5A4-34 ANTI-LOCK BRAKE SYSTEM (ABS)

SYMPTOM DIAGNOSIS

Symptom Diagnosis

The symptoms that cannot be indicated by the warning light can be divided in the following five categories:

1. ABS works frequently but vehicle does not decelerate.
2. Uneven braking occurs while ABS works.
3. The wheels lock during braking.
4. Brake pedal feel is abnormal.
5. ABS operating sound (from Hydraulic Unit) is heard while not braking.

These are all attributable to problems which cannot be detected by EHCU self-diagnosis. Use the customer complaint
and a test to determine which symptom is present. Then follow the appropriate flow chart listed below.

Chart A-1 ABS Works Frequently But Vehicle Does Not Decelerate

No.

Symptom

Diagnostic Flow Charts

Without Tech 2

With Tech 2

1

ABS works frequently but vehicle does not decelerate.

Chart A-1

Chart TA-1

2

Uneven braking occurs while ABS works.

Chart A-2

Chart TA-2

3

The wheels are locked.

Chart A-3

Chart TA-3

4

ABS operating sound (from Hydraulic Unit) is heard while not
braking.

Chart A-4

Chart TA-4

Step

Action

Value(s)

YES

NO

1

Inspect the tires.

Are tire sizes as specified?

Isn’t there any abnormal wear?

—

Go to Step 2

Repair tires.

Go to Step 2

2

Is braking force distribution normal between
the front and rear of the vehicle?

—

Go to Step 3

Repair brake

parts.

Go to Step 7

3

Are axle parts installed normally?

—

Go to Step 4

Repair axle parts.

Go to Step 7

4

Is there play in each wheel speed sensor?

—

Go to Step 5

Repair wheel

speed sensor.

Go to Step 7

5

Is there damage, or powdered iron sticking to
each wheel speed sensor/sensor rotor?

—

Go to Step 6

Replace sensor or

sensor rotor.
Go to Step 7

6

Is the output of each wheel speed sensor nor-
mal? (Refer to chart C-1-1 to C-1-4 or TC-1)

—

Replace EHCU.

Go to Step 7

Replace wheel

speed sensor or

repair harness.

Go to Step 7

7

Reconnect all components and ensure all
components are properly mounted.

Was this step finished?

—

Repeat the “Basic

diagnostic flow

chart”.

—

ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-35

Chart TA-1 ABS Works Frequently But Vehicle Does Not Decelerate (Use Tech 2)

Chart A-2 Uneven Braking Occurs While ABS Works

Step

Action

Value(s)

YES

NO

1

Return to Chart A-1.

Was the Chart A-1 from Step 1 to Step 4 fin-
ished?

—

Go to Step 2

Repair tires.

Go to Step 1

2

1. Connect Tech 2.
2. Confirm the output from each wheel sen-

sor on DATA DISPLAY.

Is the minimum vehicle speed output from
each sensor stable at 4 km/h (3 mph) or less?

—

Go to Step 3

Replace wheel

speed sensor.

Go to Step 4

3

Return to Chart A-1.

Was the Chart A-1 finished?

—

Go to Step 4

Go to Step 3

4

Reconnect all components, ensure all compo-
nents are properly mounted.

Was this step finished?

—

Repeat the “Basic

diagnostic flow

chart”.

—

Step

Action

Value(s)

YES

NO

1

Is there play in each sensor?

—

Go to Step 2

Repair.

Go to Step 5

2

Damage or powdered iron sticking to each
sensor/sensor rotor?

—

Go to Step 3

Repair.

Go to Step 5

3

Is the output of each sensor normal? (Refer to
chart C-1-1 to C-1-4 or TC-1)

—

Go to Step 4

Replace sensor or

repair harness.

Go to Step 5

4

Is brake pipe connecting order correct?

—

Replace EHCU.

Go to Step 5

Reconnect brake

pipe correctly.

Go to Step 5

5

Reconnect all components, ensure all compo-
nents are properly mounted.

Was this step finished?

—

Repeat the “Basic

diagnostic flow

chart”.

—

5A4-36 ANTI-LOCK BRAKE SYSTEM (ABS)

Chart TA-2 Uneven Braking Occurs While ABS Works (Use Tech 2)

Chart A-3, TA-3 The Wheels Are Locked

Step

Action

Value(s)

YES

NO

1

1. Connect Tech 2.
2. WHEEL SENSORS make sure of the out-

put conditions of each sensor.

Is the output of each sensor normal?

—

Go to Step 2

Replace wheel

speed sensor.

Go to Step 3

2

Check the brake pipe connecting.

Is brake pipe connecting order correct?

—

Replace EHCU.

Go to Step 4

Repair brake pipe.

Go to Step 4

3

Check the wheel speed sensor and repair if
necessary (Refer to chart C-1-1 to C-1-4 or
TC-1).

Is each chart complete?

—

Go to Step 4

Go to Step 3

4

Reconnect all components, ensure all compo-
nents are properly mounted.

Was this step finished?

—

Repeat the “Basic

diagnostic flow

chart”.

—

Step

Action

Value(s)

YES

NO

1

Is ABS working?

—

Go to Step 2

Go to Step 4

2

Is vehicle speed under 10 km/h (6 mph)?

—

Go to Step 3

Normal.

3

Is sensor output normal? (Chart C-1-1 to C-1-4
or TC-1)

—

Go to Step 4

Replace sensor or

repair harness.

Go to Step 5

4

Is hydraulic unit grounded properly?

—

Replace hydraulic

unit.

Go to Step 5

Correct.

Go to Step 5

5

Reconnect all components, ensure all compo-
nents are properly mounted.

Was this step finished?

—

Repeat the “Basic

diagnostic flow

chart”.

—