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 

-