warning ISUZU TF SERIES 2004 Workshop Manual

SUPPLEMENTAL RESTRAINT SYSTEM 9A-1

RESTRAINTS
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
SERVICING
PAGE
Service Precaution ............................................................................................................ 9A- 3
General Description ...................................................................................................... 9A- 4
Restraint Devices ..................................................................................................... 9A- 4
System Description .................................................................................................. 9A- 5
SRS Component And Wiring Location View ............................................................... 9A- 6
Component Description ............................................................................................... 9A- 8
SRS Control Unit ...................................................................................................... 9A- 8
"Air Bag" Warning Lamp.......................................................................................... 9A- 8
SRS Coil Assembly................................................................................................... 9A- 9
Air Bag Assemblies .................................................................................................. 9A- 9
Seat Belt with Pretensioner (If so equipped) ......................................................... 9A- 10
Steering Column ....................................................................................................... 9A- 10
Knee Bolster ............................................................................................................. 9A- 10
Definitions...................................................................................................................... 9A- 10
Diagnosis .......................................................................................................................9A- 12
Diagnostic Trouble Codes ....................................................................................... 9A- 12
Scan Tool Diagnostics ............................................................................................. 9A- 12
Use Of Special Tools ................................................................................................ 9A- 12
SRS Connector Body Face Views................................................................................ 9A- 13
Repairs And Inspections Required After An Accident ............................................... 9A- 14
Accident With Deployment-Component Replacement And Inspections ............. 9A- 14
Accident With or Without Deployment-Component Inspection ........................... 9A- 14
SRS Control Unit Replacement Guidelines ............................................................ 9A- 14
Wiring Damage ......................................................................................................... 9A- 14
SRS Connector (Plastic Body And Terminal Metal Pin) Damage ......................... 9A- 14
SRS Wire Pigtail Damage......................................................................................... 9A- 14

9A-4 SUPPLEMENTAL RESTRAINT SYSTEM

Service Precaution
WARNING: THIS VEHICLE HAS A SUPPLEMENTAL
RESTRAINT SYSTEM (SRS). REFER TO THE SRS
COMPONENT AND WIRING LOCATION VIEW IN
ORDER TO DETERMINE WHETHER YOU ARE
PERFORMING SERVICE ON OR NEAR THE SRS
COMPONENTS OR THE SRS WIRING. WHEN YOU
ARE PERFORMING SERVICE ON OR NEAR THE
SRS COMPONENTS OR THE SRS WIRING, REFE
R
TO THE SRS SERVICE INFORMATION. FAILURE
TO FOLLOW WARNINGS COULD RESULT IN
POSSIBLE AIR BAG DEPLOYMENT, PERSONAL
INJURY, OR OTHERWISE UNNEEDED SRS
SYSTEM REPAIRS.
CAUTION: Always use the correct fastener in the
proper location. When you replace a fastener, use
ONLY the exact part number for that application.
ISUZU will call out those fasteners that require a
replacement after removal. ISUZU will also call out
the fasteners that require thread lockers or thread
sealant. UNLESS OTHERWISE SPECIFIED, do not
use supplemental coatings (Paints, greases, o
r
other corrosion inhibitors) on threaded fasteners
or fastener joint interfaces. Generally, such
coatings adversely affect the fastener torque and
the joint clamping force, and may damage the
fastener. When you install fasteners, use the
correct tightening sequence and specifications.
Following these instructions can help you avoid
damage to parts and systems.
General Description
CAUTION: When fasteners are removed, always
reinstall them at the same location from which
they were removed. If a fastener needs to be
replaced, use the correct part number fastener fo
r
that application. If the correct part numbe
r
fastener is not available, a fastener of equal size
and strength (or stronger) may be used.
Fasteners that are not reused, and those requiring
thread locking compound will be called out. The
correct torque value must be used when installing
fasteners that require it. If the above conditions
are not followed, parts or system damage could
result.


Restraint Devices
827RW006
Legent
(1) Deployed Air Bag
(2) Knee Bolster
(3) Seat Belt


The Supplemental Restraint System (SRS) helps
supplement the protection offered by the driver and
front passenger seat belts by deploying an air bag
from the center of the steering wheel and from the
front of the passenger side of the instrument panel.
The air bag deploys when the vehicle is involved in a
frontal crash of sufficient force up to 30 degrees off the
centerline of the vehicle. To further absorb the crash
energy there is a knee bolster located beneath the
instrument panel for both the driver and passenger,
and the steering column is collapsible.

827RW005

SUPPLEMENTAL RESTRAINT SYSTEM 9A-5

System Description
The SRS consists of the SRS control unit, the driver
air bag assembly, the SRS coil assembly, the
passenger air bag assembly and the “AIR BAG”
warning lamp in the instrument cluster. The SRS
control unit, SRS coil assembly (driver side only),
driver air bag assembly, passenger air bag assembly
and connector wire make up the deployment loops.
The function of the deployment loops is to supply
current through air bag assembly, which will cause
deployment of the air bags in the event of a frontal
crash of sufficient force, up to 30 degrees off the
centerline of the vehicle. The air bag assemblies are

only supplied enough current to deploy when the SRS
control unit detects vehicle velocity changes severe
enough to warrant deployment.
The SRS control unit contains a sensing device which
converts vehicle velocity change to an electrical signal.
The electrical signal generated is processed by the
SRS control unit and then compared to a value stored
in memory. When the generated signal exceeds the
stored value, the SRS control unit will cause current to
flow through the air bag assembly deploying the air
bags.



RTW49JLF000101

9A-8 SUPPLEMENTAL RESTRAINT SYSTEM

The SRS control unit is connected to the SRS wiring
harness by a 52–pin connector. This harness
connector uses a shorting clip across certain terminals
in the contact area. This shorting clip connects the
“AIR BAG” warning lamp to ground when the SRS
control unit harness connector is disconnected or CPA
(Connector Position Assurance) is not inserted even if
completely connected. This will cause the “AIR BAG”
warning lamp to come “ON” steady whenever the
ignition switch is at the ON or START positions with
the SRS control unit disconnected.


060R300008
Legent
(1) SRS Control Unit
(2) SRS Harness
(3) Connector Position Assurance

Component Description
SRS Control Unit
WARNING: DURING SERVICE PROCEDURES, BE
VERY CAREFUL WHEN HANDLING A SRS
CONTROL UNIT NEVER STRIKE OR JAR THE SRS
CONTORL UNIT. NEVER POWER UP THE SRS
WHEN THE SRS CONTROL UNIT IS NOT RIGIDLY
ATTACHED TO THE VEHICLE. ALL SRS
CONTROL UNIT AND MOUNTING BRACKET
FASTENERS MUST BE CAREFULLY TORQUED
AND THE ARROW MUST BE POINTED TOWARD
THE FRONT OF THE VEHICLE TO ENSURE
PROPER OPERATION OF THE SRS. THE SRS
CONTROL UNIT COULD BE ACTIVATED WHEN
POWERED WHILE NOT RIGIDLY ATTACHED TO
THE VEHICLE WHICH COULD CAUSE
DEPLOYMENT AND RESULT IN PERSONAL
INJURY.
The SRS control unit is designed to perform the
following functions in the SRS:
1. Energy Reserve — The SRS control unit maintains
24–
Volt Loop Reserve (24VLR) energy supply to
provide deployment energy when ignition voltage is
lost in a frontal crash.
2. Frontal Crash Detection — The SRS control uni
t
monitors vehicle velocity changes to detect frontal
crashes which are severe enough to warran
t
deployment.
3. Air Bag Deployment — When a frontal crash o
f
sufficient force is detected, the SRS control unit
will cause enough current to flow through the air
bag assembly to deploy the air bag.
4. Malfunction Detection —The SRS control uni
t
performs diagnostic monitoring of SRS electrical
components and sets a diagnostic trouble code
when a malfunction is detected.
5. Frontal Crash Recording — The SRS control uni
t
records information regarding SRS status during
frontal crash.
6. Malfunction Diagnosis —The SRS control uni
t
displays SRS diagnostic trouble codes and system
status information through the use of a scan tool.
7. Driver Notification — The SRS control unit warns
the vehicle driver of SRS malfunctions b
y
controlling the “Air Bag” warning lamp.




“Air Bag” Warning Lamp
Ignition voltage is applied to the “AIR BAG” warning
lamp when the ignition switch is at the ON or START
positions. The SRS control unit controls the lamp by
providing ground with a lamp driver. The “AIR BAG”
warning lamp is used in the SRS to do the following:
1.
Verify lamp and SRS control unit operation by
flashing SEVEN (7) times when the ignition switch
is first turned “ON”.
2. Warn the vehicle driver of SRS electrical system
malfunctions which could potentially affect the
operation of the SRS. These malfunctions could
result in nondeployment in case of a frontal crash
or deployment for conditions less severe than
intended.
The “AIR BAG “ warning lamp is the key to driver
notification of SRS malfunctions. For proper lamp
operation, refer to the “SRS Diagnostic System Check”
in this section.

9A-10 SUPPLEMENTAL RESTRAINT SYSTEM

060R300013

Seat Belt with Pretensioner (If so
equipped)
The seat belt comprises a seat belt and a cylinder (a
cylinder filled with powder and an ignition device). In
cases of frontal collision which cause a shock
exceeding a specified level, the controller lets current
flow to the inflation circuit. The current ignites the
cylinder of the seat belt, producing gas. The gas helps
tighten the seat belt to restrain firmly the driver’s upper
half in his seat.




RTW49JSH000201







Steering Column
The steering column absorbs energy and is designed
to compress in a frontal crash to decrease the chance
of injury to the driver.
060R300038

Knee Bolster
The knee bolsters are used to absorb energy to
protect knees and control the forward movement of
the vehicle's front seat occupants during a frontal
crash, by limiting leg movement.

Definitions
Air Bag
An inflatable cloth cushion designed to deploy in
certain frontal crashes. It supplements the protection
offered by the seat belts by distributing the impact load
more evenly over the vehicle occupant's head and
torso.
Asynchronous
Performed in a nonperiodic fashion, (i.e., no defined
time or interval).
B+
Battery voltage, (B+) The voltage available at the
battery at the time of the indicated measurement.
With the key “ON” and the engine not running, the
system voltage will likely be between 12 and 12.5
volts. At idle, the voltage may be 14 to 16 volts. The
voltage could be as low as 10 volts during engine
cranking.
Bulb Check
The SRS control unit will cause the “AIR BAG” warning
lamp to flash seven times and then go “OFF”
whenever the ignition switch transitions to the ON
position from any other ignition switch position and no
malfunctions are detected.

9A-12 SUPPLEMENTAL RESTRAINT SYSTEM

Diagnosis
WARNING: TO AVOID DEPLOYMENT WHEN
TROUBLESHOOTING THE SRS, DO NOT USE
ELECTRICAL TEST EQUIPMENT SUCH AS A
BATTERY–POWERED OR AC–POWERED
VOLTMETER, OHMMETER, ETC., OR ANY TYPE
OF ELECTRICAL EQUIPMENT OTHER THAN THAT
SPECIFIED IN THIS MANUAL. DO NOT USE A
NONPOWERED PROBE–TYPE TESTER.
INSTRUCTIONS IN THIS MANUAL MUST BE
FOLLOWED CAREFULLY, OTHERWISE
PERSONAL INJURY MAY RESULT.
Diagnostic Trouble Codes
The “SRS Diagnostic System Check” must always be
the starting point of any SRS diagnosis. The “SRS
Diagnostic System Check” checks for proper “AIR
BAG” warning lamp operation and checks for SRS
diagnostic trouble codes using the scan tool.
1. Current diagnostic trouble codes – Malfunctions
that are presently being detected. Curren
t
diagnostic trouble codes are stored in RAM
(Random Access Memory).
2. History diagnostic trouble codes – All malfunctions
detected since the last time the history memor
y
was cleared. History diagnostic trouble codes are
stored in EEPROM.


Scan Tool Diagnostics
A scan tool is used to read current and history
diagnostic trouble codes and to clear all diagnostic
trouble codes after a repair is completed. The scan
tool must be updated to communicate with the SRS
through a replaceable cartridge before it can be used
for SRS diagnostics. To use the scan tool, connect it
to the data link connector and turn the ignition switch
“ON”. The scan tool reads serial data from the SRS
control unit “Serial Data” line terminal “21” to the data
link connector terminal “2”.

Use Of Special Tools
WARNING: TO AVOID DEPLOYMENT WHEN
TROUBLESHOOTING THE SRS, DO NOT USE
ELECTRICAL TEST EQUIPMENT SUCH AS A
BATTERY–POWERED OR AC–POWERED
VOLTMETER, OHMMETER, ETC, OR ANY TYPE OF
ELECTRICAL EQUIPMENT OTHER THAN THAT
SPECIFIED IN THIS MANUAL. DO NOT USE A NON
POWERED PROBE–TYPE TESTER.
INSTRUCTIONS IN THIS MANUAL MUST BE
FOLLOWED CAREFULLY, OTHERWISE
PERSONAL INJURY MAY RESULT. YOU SHOULD
BE FAMILIAR WITH THE TOOLS LISTED IN THIS
SECTION UNDER THE HANDLING SRS SPECIAL
TOOLS.
You should be able to measure voltage and
resistance. You should be familiar with proper use of
a scan tool such as the Tech 2 Diagnostic Computer,
SRS Driver/Passenger Load Tool 5-8840-2421-0,
Connector Test Adapter Kit 5-8840-0385-0 and the
DVM (Digital Multimeter) 5-8840-0285-0.

SUPPLEMENTAL RESTRAINT SYSTEM 9A-13

SRS Connector Body Face Views

RTW49JMF000201
Legend
(1) SRS control unit
(2) Driver Air Bag Assembly
(3) Passenger Air Bag Assembly (4) “Air Bag” Warning Lamp
(5) DLC
(6) Pretensioner Seat Belt

9A-14 SUPPLEMENTAL RESTRAINT SYSTEM

Repairs And Inspections Required
After An Accident
If any SRS components are damaged, they must be
replaced. If SRS component mounting points are
damaged, they must be replaced.
 Never use SRS parts from another vehicle. This
does not include remanufactured parts purchased
from an authorized dealer; they may be used fo
r
SRS repairs.
 Do not attempt to service the SRS control unit, the
SRS coil assembly, or the air bag assembly.
Service of these items is by replacement only.

Verify the part number of replacement air bag
assembly.

CAUTION: Never use the air bag assembly from
another vehicle and difference model year air bag
assembly.
Use only new air bag assembly proper to the
TFR/S which is being repaired.
CAUTION: Proper operation of the sensors and
supplemental restraint system (SRS) requires that
any repairs to the vehicle structure return it to the
original production configuration. Deployment
requires, at a minimum, replacement of the SRS
control unit, air bag assembly and dimensional
inspection of the steering column. Any visible
damage to the SRS control unit mounting bracket
(s) requires replacement, and the steering column
must be dimensionally inspected, whethe
r
deployment occurred or not.
Accident With Deployment – Component
Replacement And Inspections
Certain SRS components must be replaced or
inspected for damage after a frontal crash involving air
bag deployment. Those components are:
 Air bag assembly
 SRS control unit

CAUTION: Refer to “SRS control unit
Replacement Guidelines” below for important
information on SRS control unit replacement in
both deployment and non deployment crashes.
 SRS coil assembly — Inspect wiring and connecto
r
for any signs of scorching, melting, or damage due
to excessive heat. Replace if damaged. Refer to
section “SRS Coil Assembly” in this manual.
Accident With or Without Deployment –
Component Inspection
Certain SRS system components and rotation parts
must be inspected after any crash, whether the air bag
deployed or not. Those components are:
 Steering column —Refer to Inspection Required
“After an Accident” in this manual.
 Knee bolsters and mounting points —Inspect fo
r
any distortion, bending, cracking, or other damage.
 I/P steering column reinforcement plate —Inspect
for any distortion, bending, cracking, or othe
r
damage.
 I/P braces —Inspect for any distortion, bending,
cracking, or other damage.
 Seat belts and mounting points — Refer to “Seat
Belts” in Section “Seat Belt” of this workshop
manual.

SRS Control Unit Replacement Guidelines
SRS control unit replacement policy requires
replacement of SRS control unit, after crash involving
air bag deployment when “SRS Warning Lamp” turn
“ON”, “SRS Diagnosis” should be done according to
Section “Restraint Control System.”

Wiring Damage
If any SRS wire harness is damaged, it should be
replaced. Don't repair SRS harness. It is replace only.

SRS Connector (Plastic Body And
Terminal Metal Pin) Damage
If any connector or terminal in the SRS wire harness
(except pigtails) is damaged, it should be replaced.

SRS Wire Pigtail Damage
If the wiring pigtail (a wire or wires attached directly to
the device, not by a connector) is damaged, the entire
component (with pigtail) must be replaced. Examples
of “pigtail” components are the driver air bag
assembly, the passenger air bag assembly, and the
SRS coil assembly.

SUPPLEMENTAL RESTRAINT SYSTEM 9A-15

On–Vehicle Service
Service Precaution
WARNING: WHEN PERFORMING SERVICE ON OR
AROUND SRS COMPONENTS OR SRS WIRING,
FOLLOW THE PROCEDURES LISTED BELOW TO
TEMPORARILY DISABLE THE SRS. FAILURE TO
FOLLOW PROCEDURES COULD RESULT IN
POSSIBLE AIR BAG DEPLOYMENT, PERSONAL
INJURY OR OTHERWISE UNNEEDED SRS
REPAIRS.
The SRS control unit in Driver–Passenger SRS can
maintain sufficient voltage to cause a deployment for
up to 15 seconds after the ignition switch is turned
“OFF,” the battery is disconnected, or the fuse
powering the SRS control unit is removed.
Many of the service procedures require removal of the
“SRS” fuse, and disconnection of the air bag assembly
from the deployment loop to avoid an accidental
deployment. If the air bag assembly is disconnected
from the deployment loop as noted in the “Disabling
the SRS” procedure that follows, service can begin
immediately without waiting for the 15 second time
period to expire.

Disabling The SRS
Removal
Turn the ignition switch to “LOCK” and remove key.
1. Remove SRS fuse “SRS”, from the side of the
driver side of instrument panel fuse block o
r
disconnect battery.
2. Disconnect yellow connector at the base o
f
steering column.
3. Remove glove box assembly, refer to “Passenge
r
Air Bag Assembly Replacement” in this manual.
4. Disconnect yellow connector behind the glove box
assembly.
CAUTION: With the “SRS” fuse removed and
ignition switch “ON”, the “AIR BAG” warning lamp
will be “ON”. This is normal operation and does
not indicate an SRS malfunction.

Enabling The SRS
Installation
CAUTION: Never use the air bag assembly from
another vehicle and difference model year air bag
assembly.
Use only new air bag assembly proper to the
TFR/S which is being repaired.
Turn ignition switch to “LOCK” and remove key.
1. Connect yellow connector passenger air bag
assembly.
2. Install glove box assembly. Refer to “Passenger ai
r
bag assembly replacement” in this manual.
3. Connect yellow connector at the base of steering
column.
4. Install “AIR BAG” fuse “SRS” to the side of the
driver side of instrument panel fuse block o
r
connect battery.
Turn ignition switch to “ON” and verify that the “AIR
BAG” warning lamp flashes seven times and then
turns “OFF.” If it does not operate as described,
perform the “SRS Diagnostic System Check” in this
manual.

Handling / Installation / Diagnosis
1. Air bag assembly should not be subjected to
temperatures above 65

C (150
F).
2.
Air bag assembly, and SRS control unit should not
be used if they have been dropped from a height
of 100 centimeters (3.28 feet) or more.
3. When a SRS control unit is replaced, it must be
oriented with the arrow on the sensor pointing
toward the front of the vehicle. It is very important
for the SRS control unit to be located flat on the
mounting surface, parallel to the vehicle datum
line. It is important that the SRS control unit
mounting surface is free of any dirt or other foreign
material.
4. Do not apply power to the SRS unless all
components are connected or a diagnostic chart
requests it, as this will set a diagnostic trouble
code.
5. The “SRS Diagnostic System Check” must be the
starting point of any SRS diagnostics. The “SRS
Diagnostic System Check” will verify proper “AIR
BAG” warning lamp operation and will lead you to
the correct chart to diagnose any SRS
malfunctions. Bypassing these procedures ma
y
result in extended diagnostic time, incorrect
diagnosis, and incorrect parts replacement.

9A-16 SUPPLEMENTAL RESTRAINT SYSTEM

Air Bag Assembly Handling /
Shipping / Scrapping
Live (Undeployed) Air Bag Assembly
Special care is necessary when handling and storing a
live (undeployed) air bag assembly. The rapid gas
generation produced during deployment of the air bag
could cause the air bag assembly, or an object in front
of the air bag assembly, to be thrown through the air in
the unlikely event of an accidental deployment.

060R300011
WARNING: WHEN CARRYING A LIVE AIR BAG
ASSEMBLY, MAKE SURE THE BAG OPENING IS
POINTED AWAY FROM YOU. IN CASE OF AN
ACCIDENTAL DEPLOYMENT, THE BAG WILL
THEN DEPLOY WITH MINIMAL CHANCE OF
INJURY. NEVER CARRY THE AIR BAG
ASSEMBLY BY THE WIRES OR CONNECTOR ON
THE UNDERSIDE OF THE MODULE.







827RS044
Air Bag Assembly Shipping Procedure
For Live (Undeployed) Air Bag
Assemblies
Service personnel should refer to the latest Service
Bulletins for proper SRS air bag assembly shipping
procedures.

Deployed Air Bag Assembly (Driver Side)
You should wear gloves and safety glasses. After the
air bag assembly has been deployed, the surface of
the air bag may contain a powdery residue. This
powder consists primarily of cornstarch (used to
lubricate the bag as it inflates) and by products of the
chemical reaction. Sodium hydroxide dust (similar to
lye soap) is produced as a by product of the
deployment reaction. The sodium hydroxide then
quickly reacts with atmospheric moisture and is
converted to sodium carbonate and sodium
bicarbonate (baking soda). Therefore, it is unlikely
that sodium hydroxide will be present.