Isuzu N-Series. Service manual — part 273

5A4-66 ABS/ASR

Symptom: [The ABS Operates but Pulling to One Side.] (Check Flow TA-2)

Check flow TA-2

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

NO

1

1. Connect the Tech 2.
2. Check each wheel speed sensor output.

Is each sensor output normal?

—

Go to Step2

Go to Step3

2

Check the brake pipe.

Is the pipe normal?

—

Replace the

EHCU.Go to

Step4

Repair the

pipe.Go to Step4

3

Repair and check the wheel speed sensor.
(Refer to the check flow C-1 or TC-1.)

Is this step completed?

—

Go to Step4

Go to Step3

4

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

Is this step completed?

—

Repeat “Diagnos-

tic basic flow”.

Go to Step4

ABS/ASR 5A4-67

Symptom: [Wheels are Locked During Brake Operation.] (Check Flow A-3, TA-3)

Check flow A-3, TA-3

Step

Action

Value

YES

NO

1

Does the ABS operate?

—

Go to Step2

Go to Step4

2

Is the vehicle speed 10km/h (6 mph) or less?

—

Go to Step3

Normal

3

Are the wheel speed sensor outputs normal?
(Refer to the check flow C-1 or TC-1)

—

Go to Step4

Replace the sen-

sor or repair the

circuit. Go to

Step5

4

Is the EHCU grounded properly?

—

Replace the

EHCU.Go to

Step5

Repair.Go to

Step5

5

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

Is this step completed?

—

Repeat “Diagnos-

tic basic flow”.

Go to Step5

5A4-68 ABS/ASR

Symptom: [Feeling of Brake Pedal is Faulty.] (Check Flow A-4)

Check flow A-4

Step

Action

Value

YES

NO

1

Does the stop lamp come on when depress-
ing the brake pedal?

—

Go to Step2

Go to Step3

2

1. Turn the starter switch OFF.
2. Disconnect the connector of the EHCU.
3. Measure the voltage between the J-177

connector terminal 16 and the J-177 con-
nector terminal 1,23 with the brake pedal
depressed.

Is the power supply voltage supplied to it?

—

Go to Step4

Repair the circuit

between the stop

lamp switch and

the control unit.Go

to Step7

3

Is the stop lamp fuse F-5 normal?

—

Go to Step5

Replace the

fuse.Go to Step7

4

Check for continuity between the J-177 con-
nector terminal 1,23 and the body ground. Is
there continuity?

—

Go to Step6

Repair the body

ground circuit.Go

to Step7

5

Is the stop lamp switch normal?

—

Repair the stop

lamp circuit.Go to

Step7

Replace the stop

lamp switch.Go to

Step7

6

Check the suspicious circuit/connector for
improper connection. Is there improper con-
nection?

—

Brake fluid line is

leaked or air

mixed. (Refer to

Section 5A.)Go to

Step7

Repair the cir-

cuit.Go to Step7

7

Assemble all the components, and check that
those are assembled properly.

Is this step completed?

—

Repeat “Diagnos-

tic basic flow”.

Go to Step7

ABS/ASR 5A4-69

Symptom: [Brake Operating Noise Comes from the Hydraulic Unit Though the Brake Pedal
is not Depressed.] (Check Flow A-5, TA-5)

Check flow A-5, TA-5

Step

Action

Value

YES

NO

1

Is this the first time operation since the engine
is started?

—

Normal (It is a

motor check oper-
ation noise of self-

diagnosis func-

tion.)

Go to Step2

2

Is the vehicle speed 10km/h (6 mph) or less?

—

Normal (It is a

motor check oper-
ation noise of self-

diagnosis func-

tion.)

Go to Step3

3

Check for noise in the following conditions:

• When shifting down, or when operating the

clutch

• When driving a slippery low-temperature

road (iced or snow-covered), or when driv-
ing a rough road

• While turning with high speed
• When driving over a bump (such as curb-

stone)

• When operating electrical switches
• When running the engine high speed

Is noise generated in any of the above condi-
tions?

—

Normal (ABS may

operate without

depressing the

brake pedal.)

Go to Step4

4

Do all the speed sensor/sensor rotor operate
normally?

—

Go to Step5

Repair.Go to

Step7

5

Is the wheel speed sensor/sensor rotor dam-
aged? Or iron powder attached?

—

Go to Step7

Repair or replace

it.Go to Step6

6

Are all the sensor outputs normal? (Refer to
the check flow C-1 or TC-1)

—

Check the suspi-
cious circuit/con-

nector for

improper connec-

tion. If the connec-

tion is normal,

replace the

EHCU.Go to

Step7

Repair.Go to

Step7

7

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

Is this step completed?

—

Repeat “Diagnos-

tic basic flow”.

Go to Step7