Isuzu N-Series. Manual — part 272

5A4-62 ABS/ASR

List of Trouble Symptom

Troubles not appeared as warning lamp indication can
be classified into the following five categories.

1. The ABS operates frequently but brake force is in-

sufficient, or the ASR operates frequently.

2. The ABS operates but pulling to one side.
3. Wheels are locked during brake operation.
4. Feeling of brake pedal is faulty.

5. Brake operating noise comes from the EHCU

though the brake pedal is not depressed.

Self-diagnosis function is unable to detect these symp-
toms.

Check the trouble symptom by reproducing the condi-
tion through interviewing customer with the test run, and
perform the diagnosis according to each trouble symp-
tom.

Replace the EHCU.

Is this step completed?

—

Go to Step18

—

1. Install all the components, and check that

those are installed properly.

2. Clear the DTC.

Is this step completed?

—

Go to “Diagnostic

basic flow”.

Go to Step18

Step

Action

Value

YES

No.

Trouble symptom

Diagnostic check flow

Without Tech 2

With Tech 2

The ABS operates frequently but brake force is insuffi-
cient, or the ASR operates frequently.

Check flow A-1

Check flow TA-1

The ABS operates but pulling to one side.

Check flow A-2

Check flow TA-2

Wheels are locked during brake operation.

Check flow A-3

Check flow TA-3

Feeling of brake pedal is faulty.

Check flow A-4

—

Brake operating noise comes from the hydraulic unit
though the brake pedal is not depressed.

Check flow A-5

Check flow TA-5

ABS/ASR 5A4-63

Symptom: [The ABS Operates Frequently but Brake Force is Insufficient, or the ASR Oper-
ates Frequently.] (Check Flow A-1)

Check flow A-1

Step

Action

Value

YES

Check the tire.

Is the tire specification correct? Is abnormal
wear found in the outer surface?

—

Go to Step2

Replace with the

specified tire with-

out wear.Go to

Step7

Is the brake balance between front and rear
wheels correct?

—

Go to Step3

Repair the brake

components.Go to

Step7

Are the axle-related parts correctly assem-
bled?

—

Go to Step4

Repair the

parts.Go to Step7

Is the speed sensor installation normal?

—

Go to Step5

Repair the wheel

speed sensor.Go

to Step7

Is the speed sensor/sensor rotor damaged?
Or iron powder attached?

—

Go to Step6

Replace the sen-

sor or sensor

rotor. Go to Step7

Are all the wheel speed sensor outputs nor-
mal?

—

Replace the con-

trol unit.Go to

Step7

Replace the

wheel speed sen-

sor, or repair the

circuit. Go to

Step7

Install all the components, and check that
those are installed properly.

Is this step completed?

—

Repeat “Diagnos-

tic basic flow”.

Go to Step7

5A4-64 ABS/ASR

Symptom: [The ABS Operates Frequently but Brake Force is Insufficient, or the ASR Oper-
ates Frequently.] (Check Flow TA-1)

Check flow TA-1

CAUTION:

On the vehicle that the rear tires have smaller diameter,
the rear wheel speed may be indicated a little higher
than the front wheel speed. Check the speed after driv-
ing a while at a constant speed.

Step

Action

Value

YES

1. Connect the Tech 2.
2. Check each sensor output from the

“Wheel sensor”.

Is the lowest value of each wheel sensor read-
ing 4 km/h (2 mph) or less? And is the value
stable?

—

Go to Step2

Replace the

wheel speed sen-

sor.Go to Step3