ABS ISUZU TF SERIES 2004 Service Manual

BRAKE CONTROL SYSTEM 5A-21

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. When
the DTC is not detected and the ABS and BRAKE
warning lamp is on, “How to erase code” is
performed and a 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. When 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
In case that there has been an abnormality in the
lighting pattern of “ABS” warning lamp, the fault can be
located in accordance with the “DIAGNOSIS BY “ABS”
WARNING LAMP ILLUMINATION PATTERN”. In case
of such trouble as can be detected by the driver as a
vehicle symptom, however, it is necessary to give a test
drive following the test procedure mentioned below,
thereby reproducing the symptom for trouble 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 6km/h (4mph) 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 give a test drive on a wide, even road
with a small traffic.
 If an abnormality is detected, be sure to suspend
the test and start trouble diagnosis at once.

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")

5A-26 BRAKE CONTROL SYSTEM

DATA LIST (Tech 2)
The data displayed by DATA LIST are as follows:


Strings Units Description 2WD 4WD
Front Left Wheel Speed km/h (MPH)
Front Right Wheel Speed km/h (MPH)
Rear Left Wheel Speed km/h (MPH)
Rear Right Wheel Speed km/h (MPH) Start the vehicle and make sure of linear
change in each wheel speed
Brake Switch Open/Closed Brake switch is “closed” when brake pedal is
stepped on.
ABS Warning Lamp On/Off To be “Off” usually
EBD Warning Lamp On/Off To be “Off” usually
ABS Stop State On/Off To be “Off” usually
ABS Relay Active/Inactive To be “Active” usually
Return Pump Active/Inactive To be “Inactive” usually
DTC Status No DTC To be “No DTC” usually
4 Wheel Drive Status Yes/No To be “Yes” usually
-
FL Dump Valve Commanded
(Front Left) Active/Inactive
FL Isolation Valve Commanded
(Front Left) Active/Inactive
FR Dump Valve Commanded
(Front Right) Active/Inactive
FR Isolation Valve Commanded
(Front Right) Active/Inactive
Rear Dump Valve Commanded Active/Inactive
Rear Isolation Valve Commanded Active/Inactive
FL Dump Valve Feedback
(Front Left) Active/Inactive
FL Isolation Valve Feedback
(Front Left) Active/Inactive
FR Dump Valve Feedback
(Front Right) Active/Inactive
FR Isolation Valve Feedback
(Front Right) Active/Inactive
Rear Dump Valve Feedback Active/Inactive
Rear Isolation Valve Feedback Active/InactiveEach valve is “Active” when each valve is
opereted.
G-Sensor Output V 2.0~3.0V when vehicle speed is 0 km/h (flat
place) -
Battery Voltage V The voltage value currently supplied to EHCU
Diagnostics Connector Open/Closed Diagnostics connector is “Open” when
diagnostics connector is connected.

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-30 BRAKE CONTROL SYSTEM

Diagnostic Trouble Codes
Choose and trace an appropriate flowchart by the
numbers listed below to find fault and repair.
Note:
DTC cannot be erased when the DTC is a present.

Warning Lamp System Control Main Items
DTC
(Flash
Code) Description
ABS Brake
(EBD)ABS EBD
-
(12) Normal Condition




-
C0221
(21) Front Right Wheel Speed Sensor Short
Circuit or Circuit Open

*A

Sensor or Wiring
C0222
(22) Front Right Wheel Speed Sensor
Incorrect Signal *B

A

Sensor or install condition
C0223
(23) Front Right Wheel Speed Sensor Signal
- Tooth Chipping

*A

Sensor Rotor or install
condition
C0225
(25) Front Left Wheel Speed Sensor Short
Circuit or Circuit Open

*A

Sensor or Wiring
C0226
(26) Front Left Wheel Speed Sensor
Incorrect Signal *B

*A

Sensor or install condition
C0227
(27) Front Left Wheel Speed Sensor Signal -
Tooth Chipping

*A

Sensor Rotor or install
condition
C0231
(31) Rear Right Wheel Speed Sensor Short
Circuit or Circuit Open

*A

Sensor or Wiring
C0232
(32) Rear Right Wheel Speed Sensor
Incorrect Signal *B

*A

Sensor or install condition
C0233
(33) Rear Right Wheel Speed Sensor Signal
- Tooth Chipping

*A

Sensor Rotor or install
condition
C0235
(35) Rear Left Wheel Speed Sensor Short
Circuit or Circuit Open

*A

Sensor or Wiring
C0236
(36) Rear Left Wheel Speed Sensor
Incorrect Signal *B

*A

Sensor or install condition
C0237
(37) Rear Left Wheel Speed Sensor Signal -
Tooth Chipping

*A

Sensor Rotor or install
condition
C0238
(38) Tire Diameter Error



Vehicle , Sensor or Tire
C0241
(41) Front Right Isolation Solenoid Circuit
Open or Shorted to Ground



Solenoid (EHCU)
C0242
(42) Front Right Dump Solenoid Circuit
Open or Shorted to Ground



Solenoid (EHCU)
C0243
(43) Front Right Isolation Solenoid Circuit
Shorted to Battery



Solenoid (EHCU)
C0244
(44) Front Right Dump Solenoid Circuit
Shorted to Battery



Solenoid (EHCU)
C0245
(45) Front Left Isolation Solenoid Open Or
Shorted to Ground



Solenoid (EHCU)
C0246
(46) Front Left Dump Solenoid Circuit Open
Or Shorted to Ground



Solenoid (EHCU)
C0247
(47) Front Left Isolation Solenoid Circuit
Shorted to Battery



Solenoid (EHCU)

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.

5A-32 BRAKE CONTROL SYSTEM

Diagnosis By “ABS” Warning Lamp
Illumination Pattern
In the event that there is abnormality in the “ABS”
warning Lamp illumination pattern while the key is in the
ON position or if the warning Lamp is actuated during
driving, trouble should be diagnosed on a illumination
pattern basis as follows:

No. Condition “ABS” Warning Lamp Illumination Pattern Diagnostic
1 Warning Lamp is
actuated normally
Normal
2 Warning Lamp is not
lit
Warning Lamp lighting circuit
trouble. Go to No ABS
Warning Lamp.
3 Warning Lamp
remains ON
Diagnostic trouble codes are
stored.
Display diagnostic trouble
codes and diagnose on a
code basis according to
the flow charts.
4 Warning Lamp is
actuated while driving
Diagnostic trouble codes are
stored.
Display diagnostic trouble
codes and diagnose on a
code basis according to
the flow charts.

Diagnostic Trouble Codes (DTCs)
When the warning lamp in the meter remains ON, the
EHCU stores the fault identification and disables the
ABS.

5A-34 BRAKE CONTROL SYSTEM

4. Notes
 If the following should occur during Diagnostic
Trouble Code (DTC) display, the display will be
discontinued. After initial check, the status that
is under the control of ABS will be returned :
– The vehicle starts (The wheels turn) or the
brake pedal is depressed.
 Up to 3 different codes can be stored.
 If the ABS should turn OFF due to an
intermittent defect, the system will be restored
at the next key cycle, if the initial check finds no
abnormality (when IGN is switched from OFF to
ON).
5. An example of DTC display
Display of DTC 23

B05R100001
After displaying DTC 12 three times, one DTC after
another is displayed. DTC is displayed on small
order.

C05L300017
The DTC 12 is displayed repeatedly.

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

BRAKE CONTROL SYSTEM 5A-37

Basic Inspection Procedure
1. Basic Inspection of Service Brake
Step Action
Value(s) Yes No
1 Is the fluid level normal?
- Go to Step 2 Replenish with
fluid
Go to Step 2
2 Does fluid leak?
- Repair
Go to Step 3 Go to Step 3
3 Is the booster function normal?
- Go to Step 4 Repair
Go to Step 4
4 Is the pad and rotor normal?
- Go to Step 5 Repair
Go to Step 5
5 Reconnect all components. Ensure all component
are properly mounted.
Was this step finished? - Finished Go to Step 5

2. Ground Inspection
Step Action
Value(s) Yes No
1 Does ABS related ground points normally?
- Go to Step 2 Repair
Go to Step 2
2 Reconnect all components. Ensure all component
are properly mounted.
Was this step finished? - Finished Go to Step 2