Isuzu KB P190. Manual — part 159

BRAKE CONTROL SYSTEM 5A-43

Uneven Braking Occurs While ABS Works

Step Action Value(s)

Yes No

1

Is there play in each or any sensor?

-

Repair.

Go to Step 5

Go to Step 2

2

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

-

Repair.

Go to Step 5

Go to Step 3

3

Is the output normal for each sensor?

-

Go to Step 4

Replace

sensor or

repair

harness.

Go to Step 5

4

Is brake pipe connecting order correct?

Note: Check the EHCU type for specification, when
the EHCU is replaced.

(Specification; 2WD Model or 4WD Model)

-

Replace

EHCU.

Go to Step 5

Reconnect

brake pipe

correctly.

Go to Step 5

5

Reconnect all components, ensure all components
are properly mounted.

Is this step finished?

-

Repeat the

“Basic

diagnostic

flow chart”

Go to Step 5

The Wheels Are Locked

Step Action Value(s)

Yes

No

1

Is ABS working?

-

Go to Step 2

Go to Step 4

2

Is vehicle speed under 5 km/h?

-

Go to Step 3

Normal.

3

Is the output for each normal?

-

Go to Step 4

Replace

sensor or

repair

harness.

Go to Step 6

4

Is 2-4WD system function normal?

-

Go to Step 5

Replace 2-

4WD control
unit or repair

harness.

Go to Step 6

5

Is EHCU grounded properly?

Note: Check the EHCU type for specification, when
the EHCU is replaced.

(Specification; 2WD Model or 4WD Model)

-

Replace

EHCU.

Go to Step 6

Repair.

Go to Step 6

6

Reconnect all components, ensure all components
are properly mounted.

Is this step finished?

-

Repeat the

“Basic

diagnostic

flow chart”

Go to Step 6

5A-44 BRAKE CONTROL SYSTEM

Brake Pedal Feed Is Abnormal

Step Action Value(s) Yes

No

1

Is the stop light actuated when the brake pedal is
depressed?

-

Go to Step 2

Go to Step 3

2

1. Turn the ignition switch off.

2. Disconnect EHCU connector.

Is the check voltage for EHCU connector terminals
when brake pedal is depressed than battery voltage?

-

Go to Step 4

Harness NG

between stop

light SW and

EHCU.

Go to Step 6

3

Is stop light fuse normal?

-

Go to Step 5

Replace stop

light fuse.

Go to Step 6

4

Is the check continuity between EHCU connector to
body grounded?

-

Go to Step 6

Repair body

grounded

harness.

Go to Step 6

5

Is stop light switch operation normal?

-

Repair stop

light harness.

Go to Step 6

Replace stop

light switch.

Go to Step 6

6

Reconnect all components, ensure all components
are properly mounted.

Is this step finished?

-

Repeat the

“Basic

diagnostic

flow chart”

Go to Step 6

BRAKE CONTROL SYSTEM 5A-45

Braking Sound (From EHCU) Is Heard While Not Braking

Step Action Value(s)

Yes

No

1

Is this the first vehicle start after engine start?

-

It is self

checking

sound

Normal.

Go to Step 2

2

Is vehicle speed at 15 km/h or 30 km/h?

-

It is self

checking

sound

Normal.

Go to Step 3

3

Check for the following condition:

• At the time of shift down or clutch operation.

• At the time of low road friction drive (ice or snow on

road) or rough road drive.

• At the time of high-speed turn.

• At the time of passing curb.

• At the time of operating electrical equipment

switches.

• At the time of racing the engine.

Did it occur under any of the conditions above?

-

ABS may

sometimes be
actuated even

when brake

pedal is not

applied.

Go to Step 4

4

Is there play in each or any sensor/wheel speed
sensor rotor?

-

Repair.

Go to Step 7

Go to Step 5

5

Damage or powdered iron sticking to each or any
sensor/wheel speed sensor rotor?

-

Repair.

Go to Step 7

Go to Step 6

6

Is each sensor normal?

Note: Check the EHCU type for specification, the
EHCU is replaced.

(Specification; 2WD or 4WD Model)

-

Check

harness/

connector for

suspected

disconnection

If no

disconnection

is found,

replace EHCU

Go to Step 7

Repair.

Go to Step 7

7

Reconnect all components, ensure all components
are properly mounted.

Is this step finished?

-

Repeat the

“Basic

diagnostic

flow chart”

Go to Step 7

5A-46 BRAKE CONTROL SYSTEM

No ABS Warning Lamp

Step Action Value(s) Yes

No

1

Check the meter fuse for the instrument cluster
ignition feed circuit.

Is the fuse OK?

-

Go to Step 3

Go to Step 2

2

Replace the fuse.

Is the action complete?

-

Verify repair

Go to Step 3

-

3

1. Ignition “OFF”, disconnect the EHCU.

2. Ignition “ON”, engine “OFF”.

3. Observe the ABS warning lamp.

Is the ABS warning lamp “ON”?

-

Go to Step 5

Go to Step 4

4

Repair or replace the meter circuit or meter.

Is the action complete?

-

Verify repair

-

5

1. Check the EHCU circuit for an open, short to

ground, or short to voltage. Also, check the EHCU
ignition feed circuit for an open or short to ground
and the EHCU ground circuit for an open.

2. If a problem is found, repair as necessary.

Was a problem found?

-

Verify repair

Go to Step 6

6

1. Ignition “OFF”, reconnect the EHCU.

2. Ignition “ON”,engine “OFF”.

3. Observe the ABS warning lamp.

Is the ABS warning lamp “ON”?

-

Verify repair

Go to Step 7

7 Replace

EHCU.

Note: Check the EHCU type for specification, the
EHCU is replaced.

(Specification; 2WD or 4WD Model)

Is the action complete?

-

Verify repair

-