ISUZU AXIOM 2002 Service Repair Manual

5A±12BRAKE CONTROL SYSTEM
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 suspected
circuits for damage:

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 of an intermittent ABS lamp illumination, see
ªDiagnosis by ABS Warning Light illumination Patternº or
go to 5A±37. In some cases, the vehicle may need to be
test driven by following the test procedure below.
1. Start the engine and make sure that the ªABSº 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 12 km/h (8 mph) 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 ªSYMPTOM DIAGNOSISº .
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.
ªABSº Warning Light
When ABS trouble occurs to actuate ªABSº warning light,
the trouble code corresponding to the trouble is stored in
the EHCU. Only ordinary brake is available with ABS
being unactuated. Even when ªABSº warning light 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 light is lit normally even though the trouble
code is stored.
NOTE: Illumination of the ªABSº warning light indicates
that anti-lock braking is no longer available. Power
assisted braking without anti-lock control is still available.
Normal Operation
ªABSº Warning Light
When the ignition is first moved from ªOFFº to ªRUNº , the
amber ªABSº warning light will turn ªONº . The ªABSº
warning light will turn ªONº during engine starting and will
usually stay ªONº for approximately three seconds after
the ignition switch is returned to the ªONº position. The
warning light should remain ªOFFº at all other times.

5A±13
BRAKE CONTROL SYSTEM
Tech 2 Scan Tool
From 98 MY, Isuzu dealer service departments are
recommended to use Tech 2. Please refer to Tech 2 scan
tool user guide.
901RW257
Legend
(1) PCMCIA Card
(2) SAE 16/19 Adaptor(3) DLC Cable
(4) Tech±2

5A±14BRAKE CONTROL SYSTEM
Getting Started

Before operating the Isuzu PCMCIA card with the
Tech 2, the following steps must be performed:
1. The Isuzu 98 System PCMCIA card (1) inserts into
the Tech 2 (4).
2. Connect the SAE 16/19 adapter (2) to the DLC cable
(3).
3. Connect the DLC cable to the Tech 2 (4).
4. Make sure the vehicle ignition is off.
5. Connect the Tech 2 SAE 16/19 adapter to the vehicle
DLC.
826R200011
6. The vehicle ignition turns on.
7. Power up the Tech 2.
8. Verify the Tech 2 power up display.
060RW009
Operating Procedure
The power up screen is displayed when you power up the
tester with the Isuzu systems PCMCIA card. Follow the
operating procedure below.
060R100102

5A±15
BRAKE CONTROL SYSTEM
060R200078

5A±16BRAKE CONTROL SYSTEM
DATA LIST
The data displayed by DATA LIST are as follows:
Display
ContentOK/NG Criteria for Data
Front Left Wheel Speed
Front Right Wheel Speed
Rear Wheel Speedskm/h (MPH)
Start the vehicle and make sure of linear change in
each wheel speed.

Turn each wheel by hand and make sure that each
speed data change.
Warning LampON/OFF
To be OFF usually
ABS StateON/OFF
To be OFF usually
ABS RelayActive/Inactive
To be Active usually
4 Wheel DriveActive/Inactive
2WD: Inactive

4WD: Active
Brake SwitchActive/Inactive
Inactive (Released)

Active (Pressed)
Brake Fluid LevelNormal or not
To be Normal usually
Return PumpActive/Inactive
To be Inactive usually
DRP (Dynamic Rear
Proportioning)Active/Inactive
To be Inactive usually
Rear Dump Valve CommandedActive/Inactive
To be Inactive usually
Rear Dump Valve Feedback
Rear Isolation Valve
Commanded
Rear Isolation Valve Feedback
FL Dump Valve CommandedActive/Inactive
To be Inactive usually
FL Dump Valve Feedback
FL Isolation Valve Commanded
FL Isolation Valve Feedback
FR Dump Valve CommandedActive/Inactive
To be Inactive usually
FR Dump Valve Feedback
FR Isolation Valve
Commanded
FR Isolation Valve Feedback
G±SensorVoltage
2.50V when vehicle is stopped
Battery VoltageVoltage
Between 10±16.9V

5A±17
BRAKE CONTROL SYSTEM
ACTUATOR TEST
This mode is used to exercise the ABS actuators and
make sure they operate normally. Prior to the test, pay
attention to the cautions below. (When checking the
solenoid valve system, be sure to jack up the vehicle.)
CAUTION:

Before testing, be sure that the brakes work normally.

Make sure that the battery is fully charged.Conduct
the test by two persons (A TECH 2 operator and a
vehicle checker).

Be sure to start ACTUATOR TEST with the engine
stopped.

Before testing, make sure that electrical trouble, if
any, has been completely repaired. Conducting tests
of ABS solenoid with electrical circuit problem
remaining uncorrected could damage the control unit.
F05R200001

5A±18BRAKE CONTROL SYSTEM
F05R200002

5A±19
BRAKE CONTROL SYSTEM
F05R200003

5A±20BRAKE CONTROL SYSTEM
F05R200004

5A±21
BRAKE CONTROL SYSTEM
Tech 2 Service Bleed
F05R200005