Page 617 of 6020

5A-24 BRAKE CONTROL SYSTEM
Computer System Service Precautions
The Anti-lock Brake System and Electronic Brake-force
Distribution interfaces directly with the Electronic
Hydraulic Control Unit (EHCU) which is a control
computer that is similar in some regards to the Engine
Control Module. These modules are designed to
withstand normal current draws associated with vehicle
operation. However, care must be taken to avoid
overloading any of the EHCU circuits. In testing for
opens or shorts, do not ground or apply voltage to any
of the circuits unless instructed to do so by the
appropriate diagnostic procedure. These circuits should
only be tested with a high impedance multimeter
5-8840-0366-0 or special tools as described in this
section. Power should never be removed or applied to
any control module with the ignition in the “ON” position.
Before removing or connecting battery cables, fuses or
connectors, always turn the ignition switch to the “OFF”
position.
General Service Precautions
The following are general precautions which should be
observed when servicing and diagnosing the Anti-lock
Brake System and/or other vehicle systems. Failure to
observe these precautions may result in Anti-lock Brake
System and Electronic Brake-force Distribution
damage.
• If welding work is to be performed on the vehicle using an electric arc welder, the EHCU and valve
block connectors should be disconnected before the
welding operation begins.
• The EHCU and valve block connectors should never be connected or disconnected with the
ignition “ON”.
Note:
• If only rear wheels are rotated using jacks or drum tester, the system will diagnose a speed sensor
malfunction and the “ABS and Brake” warning lamp
will illuminate. But actually no trouble exists. W hen
the DTC is not detected and the ABS and BRAKE
warning lamp is on, “How to erase code” is
performed and an ABS and BRAKE warning lamp
are off.
If the battery has been discharged
The engine may stall if the battery has been completely
discharged and the engine is started via jumper cables.
This is because the Anti-lock Brake System (ABS) and
Electronic Brake-force Distribution (EBD) System
requires a large quantity of electricity. In this case, wait
until the battery is recharged, or set the ABS and EBD
to a non-operative state by removing the fuse for the
ABS. After the battery has been recharged, stop the
engine and install the ABS fuse. Start the engine again,
and confirm that the ABS warning Lamp does not light.
Note on Intermittents
As with virtually any electronic system, it is difficult to
identify an intermittent failure. In such a case duplicating
the system malfunction during a test drive or a good
description of vehicle behavior from the customer may
be helpful in locating a “most likely” failed component or
circuit. The symptom diagnosis chart may also be
useful in isolating the failure. Most intermittent
problems are caused by faulty electrical connections or
wiring. W hen an intermittent failure is encountered,
check suspect circuits for:
• Suspected harness damage.
• Poor mating of connector halves or terminals not fully seated in the connector body (backed out).
• Improperly formed or damaged terminals.
Test Driving ABS Complaint Vehicles
If there has been an abnormality in the lighting pattern
of the “ABS” warning lamp, the fault can be located in
accordance with the “DIAGNOSIS BY “ABS” W ARNING
LAMP ILLUMINATION PATTERN”. Although such
problems can be detected by the driver as a vehicle
symptom, it is still necessary to perform a test drive
following the test procedure mentioned below, in order
to reproduce the symptom for problem diagnosis on a
symptom basis:
1. Start the engine and make sure that the “ABS” W /L
goes OFF. If the W /L remains ON, it means that
the Diagnostic Trouble Code (DTC) is stored.
Therefore, read the code and locate the fault.
Note: The DTC cannot be cleared if the vehicle speed
does not exceed about 10km/h (6mph) at DTC, even
though the repair operation is completed.
2. Start the vehicle and accelerate to about 30 km/h (19 mph) or more.
3. Slowly brake and stop the vehicle completely.
4. Then restart the vehicle and accelerate to about 40 km/h (25 mph) or more.
5. Brake at a time so as to actuate the ABS and stop the vehicle.
6. Be cautious of abnormality during the test. If the W /L is actuated while driving, read the DTC and
locate the fault.
7. If the abnormality is not reproduced by the test, make best efforts to reproduce the situation
reported by the customer.
8. If the abnormality has been detected, repair in accordance with the “SYMPTOM DIAGNOSIS”.
Note:
• Be sure to perform a test drive on a wide, even road
with light traffic.
• If an abnormality is detected, be sure to suspend the test and start trouble diagnosis at once.
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 618 of 6020

BRAKE CONTROL SYSTEM 5A-25
“ABS” Warning Lamp
W hen ABS and problems occur that actuate the “ABS”
warning lamp, the code corresponding to the problem is
stored in the EHCU. Only ordinary braking is available
when the ABS is deactivated. Even when the “ABS”
warning lamp is actuated, if the starter switch is set ON
after setting it OFF once, the EHCU checks up on the
entire system. If there is no abnormality, the EHCU
judges ABS to work correctly and the warning lamp is lit
normally, even though the problem code is stored.
NOTE: Illumination of the “ABS” warning lamp indicates
that anti-lock braking is no longer available. Power
assisted braking without anti-lock control is still
available.
Normal Operation
“ABS ” Warning Lamp
W hen the ignition is first moved from “OFF” to “RUN”,
the amber “ABS” warning lamp will turn “ON”. The
“ABS” warning lamp will turn “ON” during engine
starting and will usually stay “ON” for approximately
three seconds after the ignition switch is returned to the
“ON” position. The warning lamp should remain “OFF”
at all other times.
Brake (EBD) Warning Lamp
RTW 75ASH000101
Vehicles equipped with the EBD (Electronic Brake-force
Distribution) System have a “Brake” warning lamp on
the instrument panel.
If the ABS warning lamp and Brake warning lamp are
turned "ON", then EBD has failed. ( Parking brake
switch is "OFF")
In the following conditions, the EBD warning lamp is
"ON".
• Starter switch is "ON", engine "OFF". ( Parking brake switch is "OFF")
If engine is started, then EBD warning lamp is "OFF".
( Parking brake switch is "OFF")
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 619 of 6020
5A-26 BRAKE CONTROL SYSTEM
Tech 2 Scan Tool
Operating Procedure
The power up screen is displayed when you power
up the tester with the systems PCMCIA card. Follow
the operating procedure below.
060R100102
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 620 of 6020

BRAKE CONTROL SYSTEM 5A-27
Actuator Test
There are 8 different menus available for this test.
The state of each circuit can be tested by using these
menus. Especially when DTC cannot be detected, a
faulty circuit can be diagnosed by testing each circuit b
y
means of these menus.
Even when DTC has been detected, the circuit tests
using these menus could help discriminate between a
mechanical fault and an electrical fault.
In all cases test condition; Engine stops with the ke
y
turned to the "ON" position. To be more specific, the
test is conducted with the brake pedal stepped on afte
r
stepping once and releasing.
RTW 75ASH000201
Brake Bleed
Purpose: The purpose of this command is air bleeding
of brakes line.
Using the Tech 2 at following operation.
Air Bleeding procedure: 1. Connect the Tech 2 with the vehicle, and select "Actuator Test" menus.
2. Select a "Brake Bleed" menu from the "Actuato
r
Test" menus.
RTW 75ASH000301
3. According to indication of Tech 2 press the
"Confirm".
RTW 75ASH000401
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 621 of 6020
5A-28 BRAKE CONTROL SYSTEM
4. Check the EHCU part number. Press the "Confirm".
RTW 75ASH000501
5. Check a DTC is not detected. Press the "Confirm".
RTW 75ASH000601
6. According to indication of Tech 2 press the
"Confirm".
RTW 75ASH000701
7. According to indication of Tech 2 press the
"Confirm".
RTW 75ASH000801
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 622 of 6020

BRAKE CONTROL SYSTEM 5A-29
8. According to indication of Tech 2 press the
"Confirm".
RTW 75ASH000901
9. According to indication of Tech 2 press the
"Confirm".
RTW 75ASH001001
10. According to indication of Tech 2 press the
"Confirm".
RTW 75ASH001101
Return Pump Relay Test
Test condition: Engine stops with the key turned to the
"ON" position. To be more specific, the test is
conducted with the brake pedal stepped on afte
r
stepping once and releasing.
Test Procedure: 1. Connect the Tech 2 with the vehicle, and selec
t
"Actuator Test" menus.
2. Select a " Return Pump Relay Test " menu from the "Actuator Test" menus.
The circuit is normal if the pump motor is operated in
accordance with Tech 2 instruction.
Front Left Hold Valve Test
Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire for incorrect connections
and valve problem.
This test will help you confirm the result of your repai
r
service including the removal/ reinstallation of brake
pipe, valve line harness and valve.
Test conditions: The ignition key is in the "ON" position
with the four wheels lifted up. The brake pedal is
stepped on, released and stepped on again with the
parking brake released.
Test Procedure: 1. Connect Tech 2 with the vehicle, and selec
t
"Actuator Test" menus.
2. Select a "Front Left Hold Valve Test" menu from the "Actuator Test" menus.
3. Step on the brake pedal.
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 623 of 6020

5A-30 BRAKE CONTROL SYSTEM
4. Release the brake pedal.
5. Make sure that the front left hold solenoid valve "ON" aimed at by Tech 2 and the wheel locked
position are the same.
If different, check brake pipe, valve line harness wiring
and hydraulic unit. Repair is needed if abnormality is
found.
Front Left Release Valve Test
Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire for incorrect connections and
valve problem.
This test will help you confirm the result of your repai
r
service including the removal/ reinstallation of brake
pipe, valve line harness and valve.
Test conditions: The ignition key is in the "ON" position
with the four wheels lifted up. The brake pedal is stepped
on, released and stepped on again with the parking
brake released.
Test Procedure: 1. Connect Tech 2 with the vehicle, and select "Actuator Test" menus.
2. Select a "Front Left Release Valve Test" menu from the "Actuator Test" menus.
3. Step on the brake pedal.
4. Make sure that the front left release solenoid valve "ON" aimed at by Tech 2 and the wheel released
position are the same.
If different, check brake pipe, valve line harness wiring
and hydraulic unit. Repair is needed if abnormality is
found.
Front Right Hold Valve Test
Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire for incorrect connections and
valve problem.
This test will help you confirm the result of your repai
r
service including the removal/ reinstallation of brake
pipe, valve line harness and valve.
Test conditions: The ignition key is in the "ON" position
with the four wheels lifted up. The brake pedal is stepped
on, released and stepped on again with the parking
brake released.
Test Procedure: 1. Connect Tech 2 with the vehicle, and select "Actuator Test" menus.
2. Select a "Front Right Hold Valve Test" menu from the "Actuator Test" menus.
3. Step on the brake pedal.
4. Release the brake pedal.
5. Make sure that the front right hold solenoid valve "ON" aimed at by Tech 2 and the wheel locked
position are the same.
If different, check brake pipe, valve line harness wiring
and hydraulic unit. Repair is needed if abnormality is
found.
Front Right Release Valve Test
Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire for incorrect connections
and valve problem.
This test will help you confirm the result of your repai
r
service including the removal/ reinstallation of brake
pipe, valve line harness and valve.
Test conditions: The ignition key is in the "ON" position
with the four wheels lifted up. The brake pedal is
stepped on, released and stepped on again with the
parking brake released.
Test Procedure: 1. Connect Tech 2 with the vehicle, and selec
t
"Actuator Test" menus.
2. Select a "Front Right Release Valve Test" menu from the "Actuator Test" menus.
3. Step on the brake pedal.
4. Make sure that the front right release solenoid valve "ON" aimed at by Tech 2 and the wheel released
position are the same.
If different, check brake pipe, valve line harness wiring
and hydraulic unit. Repair is needed if abnormality is
found.
Rear Hold Valve Test
Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire for incorrect connections
and valve problem.
This test will help you confirm the result of your repai
r
service including the removal/ reinstallation of brake
pipe, valve line harness and valve.
Test conditions: The ignition key is in the "ON" position
with the four wheels lifted up. The brake pedal is
stepped on, released and stepped on again with the
parking brake released.
Test Procedure: 1. Connect Tech 2 with the vehicle, and selec
t
"Actuator Test" menus.
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007
Page 624 of 6020

BRAKE CONTROL SYSTEM 5A-31
2. Select a "Rear Hold Valve Test" menu from the
"Actuator Test" menus.
3. Step on the brake pedal.
4. Release the brake pedal.
5. Make sure that the rear hold solenoid valve "ON" aimed at by Tech 2 and the wheel locked position
are the same.
If different, check brake pipe, valve line harness wiring
and hydraulic unit. Repair is needed if abnormality is
found.
Rear Release Valve Test
Purpose: The purpose of this test is to detect brake pipe
and valve line harness wire for incorrect connections and
valve problem.
This test will help you confirm the result of your repai
r
service including the removal/ reinstallation of brake
pipe, valve line harness and valve.
Test conditions: The ignition key is in the "ON" position
with the four wheels lifted up. The brake pedal is stepped
on, released and stepped on again with the parking
brake released.
Test Procedure: 1. Connect Tech 2 with the vehicle, and select "Actuator Test" menus.
2. Select a "Rear Release Valve Test" menu from the "Actuator Test" menus.
3. Step on the brake pedal.
4. Make sure that the rear release solenoid valve "ON" aimed at by Tech 2 and the wheel released position
are the same.
If different, check brake pipe, valve line harness wiring
and hydraulic unit. Repair is needed if abnormality is
found.
BACK TO CHAPTER INDEX
TO MODEL INDEX
ISUZU KB P190 2007