engine ISUZU TF SERIES 2004 Owner's Manual

5A-22 BRAKE CONTROL SYSTEM

“ABS” Warning Lamp
When ABS and trouble occurs to actuate “ABS”
warning lamp, the trouble code corresponding to the
trouble is stored in the EHCU. Only ordinary brake is
available with ABS being unactuated. Even when
“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 and, if there is no abnormality,
judges ABS to work currently and the warning lamp is lit
normally even though the trouble 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
When 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

825L300001
Vehicles equipped with the EBD (Electronic Brake-force
Distribution) System have an have “Brake” warning
lamp in the instrument panel.
If ABS warning lamp and Brake warning lamp are turn
"ON", then EBD is failed. ( Parking brake switch is
"OFF")
In the following conditions, 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")

BRAKE CONTROL SYSTEM 5A-27

Actuator Test (Tech 2)
There are 5 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 by
means of these menus.
Even when DTC has been detected, the circuit tests
using these menus could help discriminate between a
mechanical trouble and an electrical trouble.
In all cases 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 after
stepping once and releasing.
 Engine: Stop
 Ignition SW: ON

060L300002

ABS Check Light 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 after
stepping once and releasing.
 The circuit is normal if the warning light (lamp) in
the meter panel comes on and goes out in
accordance with Tech2’s instruction.

060L300002

Return Pump 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 after
stepping once and releasing.
Make sure of the working sound of the return pump
relay and return pump.
The circuit is normal if the working sound of the return
pump relay and return pump are made in accordance
with Tech2’s instruction.

060L300002

5A-28 BRAKE CONTROL SYSTEM

Isolation Valve Test
Purpose: The purpose of this test is to detect brake
pipe and valve line harness wire for wrong connections
and valve trouble.
This test will help you confirm the result of your repair
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
Actuaor Test from the menus.
2. Select a Solenoid Valve Test Menu from the
Actuaor Test Menus.

060L300002
3. Select Isolation Valve from the Valve Select Menus.
4. Step on the brake pedal.
5. Release the brake pedal.
6. Make sure that the Isolation 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 H/UNIT. Repair is needed if abnormality
is found.
7. Conduct Step 2 through Step 5 above on all the
four wheels.

060L300002
CAUTION: When conducting this test, please
observe the following cautions.

1. Do not start the engine.
2. Lift up the vehicle at a level floor.





Secure a clearance from the floor surface
enough to allow the lifted tire to rotate.
3. Maintain the lift up.
4. Wipe the floor surface to remove water and oil
so that the surface may become unslippery.
5. Do not load the vehicle.





When lifting up the vehicle, be sure to
observe the lifting up points. Refer to
vehicle lifting points in 0A section.

BRAKE CONTROL SYSTEM 5A-29

Dump Valve Test
Purpose: The purpose of this test is to detect brake
pipe and valve line harness wire for wrong connections
and valve trouble.
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 Function from the menus.
2. Select a Solenoid Valve Test Menu from the
Actuator Test Menus.

060L300002
3. Select Dump Valve from the Valve Select Meuns.
4. Step on the brake pedal.
5. Make sure that the Dump 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 H/UNIT. Repair is needed if
abnormality is found.
6. Conduct Step 2 through Step 5 above on all the
four wheels.

060L300002
CAUTION: When conducting this test, please
observe the following cautions.

1. Do not start the engine.
2. Lift up the vehicle at a level floor.





Secure a clearance from the floor surface
enough to allow the lifted tire to rotate.
3. Maintain the lift up.
4. Wipe the floor surface to remove water and oil
so that the surface may become unslippery.
5. Do not load the vehicle.





When lifting up the vehicle, be sure to
observe the lifting up points. Refer to
vehicle lifting points in 0A section.

BRAKE CONTROL SYSTEM 5A-35

Basic Diagnostic Flow Chart

RTW45AMF000101

Step Action Value(s) Yes No
1 1. Ignition “ON,”engine “OFF.”
2. Observe the ABS warning lamp.
Note: If a starter switch is turned ON, ABS warning
lamp will turn on and a ABS warning lamp will be
turned off after 3 seconds.
Is the ABS warning lamp “ON”?
- Go to Step 2 Go to “No
ABS warning
lamp”
2 1. Ignition “OFF.”
2. Install Tech2.
3. Ignition “ON.”
4. Attempt to display ABS data with the Tech 2.
Does the Tech 2 display ABS data?
- Go to Step 5 Go to Step 3
3 1. Ignition “OFF,” disconnect the EHCU.
2. Check the DLC (Data Link Connector) circuit for an
open, short to ground, or short to voltage.
Also, check the DLC ignition feed circuit for an
open or short to ground and the DLC ground circuit
for an open.
3. If a problem is found, repair as necessary.
Was a problem found?
- Go to Step 2 Go to Step 4

5A-42 BRAKE CONTROL SYSTEM

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 under 10 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
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 one condition 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.
Was this step finished?
- Repeat the
“Basic
diagnostic
flow chart” Go to Step 7

BRAKE CONTROL SYSTEM 5A-43

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 -

5A-70 BRAKE CONTROL SYSTEM

Step Action
Value(s) Yes No
3 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 4 Verify repair
4 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

5A-72 BRAKE CONTROL SYSTEM

Step Action
Value(s) Yes No
3 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 4 Verify repair
4 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -

5A-74 BRAKE CONTROL SYSTEM

Step Action
Value(s) Yes No
3 1. Ignition “ON,” engine “OFF.”
2. Select “Display DTCs” with the Tech 2.
Note: Perform the various tests (actuator test, test
run, brake test, etc.) then observe the DTC with a
Tech2.
Are any DTCs stored? - Go to Step 4 Verify repair
4 Replace EHCU.
Note : Check the EHCU type for specification, when
the EHCU is replaced.
(Specification ; 2WD model or 4WD model)
Was the action complete? - Verify repair -