2004 ISUZU TF SERIES ignition

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-31

Warning Lamp System Control Main Items DTC
(Flash
Code) Description
ABS Brake
(EBD)ABS EBD
C0248
(48) Front Left Dump Solenoid Circuit
Shorted to Battery



Solenoid (EHCU)
C0251
(51) Rear Isolation Solenoid Circuit Open or
Shorted to Ground



Solenoid (EHCU)
C0252
(52) Rear Dump Solenoid Circuit Open or
Shorted to Ground



Solenoid (EHCU)
C0253
(53) Rear Isolation Solenoid Circuit Shorted
to Battery



Solenoid (EHCU)
C0254
(54) Rear Dump Solenoid Circuit Shorted to
Battery



Solenoid (EHCU)
C0265
(65) Fail Safe Relay (FSR) Shorted to
Ground



Motor (EHCU)
C0266
(66) Fail Safe Relay (FSR) Shorted to
Battery



Relay (EHCU)
C0267
(67) ABS Motor Shorted to Ground



Motor (EHCU)
C0268
(68) ABS Motor Shorted to Battery



Motor (EHCU)
C0271
(71) ECU Failure or Valve +B Circuit Open



EHCU
C0274
(74) ABS Operation Long Time



EHCU

C0276
(76) G-Sensor Malfunction



Sensor or Wiring




Battery, Wiring or EHCU
(less than 9V) C0277
(77) Power Supply Low Input




Battery or Wiring
(less than 10V)
C0278
(78) Power Supply High Input



Battery or Wiring EHCU
C0282
(82) 4 Wheel Drive State Input Signal Failure



Wiring
C0285
(85) Assembly Error (G-sensor)



Vehicle (Sensor or EHCU)

*A : When three or more failure are detected, or when
failure containing both front wheels and each rear
wheels are detected, EBD warning lamp is "ON"
and control is canceled.
*B : ABS lamp is “OFF” when the ABS lamp is “ON”
after a repair until vehicles speed becomes more
than 6km/h (4mph) in the following ignition cycle
and failure is not detected.

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-36 BRAKE CONTROL SYSTEM

Step Action Value(s) Yes No
4 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?
- Go to Step 2 Go to Step 11
5 Select “Display DTCs” with the Tech 2.
Are any DTCs stored? - Go to Step 6 Go to Step 10
6 Review and record for Tech 2 Failure Records data
and DTCs.
Is the action complete? - Go to Step 7 -
7 Following the DTC is stored.
Is this DTC C0271 stored?
- Go to
applicable
DTC table
after Go to
step 8 Go to Step 8
8 Clear the DTCs by “Clear the Information“ with Tech
2.
Did the DTCs cleared? - Go to Step 9 -
9 Select “Display DTCs” with the Tech 2.
Are any DTCs stored?
- Go to
applicable
DTC table Go to Step 10
10 Review and record for Tech 2 data.
Is the action complete?
- Go to
Symptom
Diagnosis and
Go to Basic
Inspection
Procedure -
11 Replace the EHCU.
Note: Check the EHCU type for specification, when
the EHCU is replaced.
(Specification; 2WD Model or 4WD Model)
Is the action complete? - Verify repair -

5A-38 BRAKE CONTROL SYSTEM

Wheel Speed Sensor Inspection Procedure
Procedure
1.Ignition "OFF".
2.Disconnect the each wheel speed sensors.
3.Check the voltage at sensor harness connector.
Note : Voltage measurement is performed in the phase
where the wheel speed sensor is installed in vehicles.

C05L300019
Connector Pin-outs

Front Wheel Speed Sensor
1 (+) (+12V)
2 (-) (signal)

Rear Wheel Speed Sensor
1 LH (+) (+12V)
2 LH (-) (signal)
3 RH (+)(+12V)
4 RH (-) (signal)






Output Value
High State 1.28~2.2V
Low State 0.5~0.86V
High-Low
Difference more than 0.8V

BRAKE CONTROL SYSTEM 5A-41

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. Disconnected 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.
Was this step finished?
- Repeat the
“Basic
diagnostic
flow chart” Go to Step 6

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 -