wiring 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

9A-6 SUPPLEMENTAL RESTRAINT SYSTEM

SRS Component And Wiring Location View - RHD






RTW49JMF000301

SUPPLEMENTAL RESTRAINT SYSTEM 9A-7

SRS Component And Wiring Location View - LHD






RTW49JMF000401

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.

SUPPLEMENTAL RESTRAINT SYSTEM 9A-9

060R300007

SRS Coil Assembly
The SRS coil assembly consists of two current
carrying coils. This is attached to the steering column
and allow rotation of the steering wheel while
maintaining continuous contact of the driver
deployment loop to the driver air bag assembly.
There is a shorting clip on the yellow connector near
the base of steering column which connects the SRS
coil to the SRS wiring harness.
The shorting clip shorts to the SRS coil and driver air
bag assembly when the yellow connector is
disconnected. The circuit to the driver air bag
assembly is shorted in this way to help prevent
unwanted deployment of the air bag when servicing
the steering column or other SRS components.
060R300047


Air Bag Assemblies
The air bag assembly consist of an inflatable air bag
assembly and an inflator. When the vehicle is in a
frontal crash of sufficient force.
The SRS control unit causes current flow through the
deployment loops. Current passing through the inflator
ignites the material in the air bag assembly. The gas
produced from this reaction rapidly inflates the air bag
assembly.
There is a shorting clip on the driver air bag assembly
connector which connects the SRS coil assembly. The
shorting clip shorts across the driver air bag assembly
circuits when driver air bag assembly connector is
disconnected.
The circuit to the driver air bag assembly is shorted in
this way to help prevent unwanted deployment of the
air bag when servicing the driver air bag assembly, the
steering column or other SRS components.

060R300012

There is a shorting clip on the passenger air bag
assembly connector which connects to the SRS
harness. The shorting clip shorts across the
passenger air bag assembly circuit when the
passenger air bag assembly connector is
disconnected. The circuit to the passenger air bag
assembly is shorted in this way to help prevent
unwanted deployment of the air bag when servicing
the passenger air bag assembly, the instrument panel
or other SRS components.

SUPPLEMENTAL RESTRAINT SYSTEM 9A-11

“Continuous Monitoring”
Tests performed by the SRS control unit on the SRS
every 100 milliseconds while “Ignition 1” voltage is in
the normal operating voltage range at the SRS control
unit.
Data Link Connector (DLC)
Formerly “DLC” a connector which allows
communication with an external computer, such as a
scan tool.
Datum Line
A base line parallel to the plane of the underbody or
frame from which all vertical measurements originate.
Deploy
To inflate the air bag.
Deployment Loops
The circuits which supply current to the air bag
assemblies to deploy the air bag.
Diagnostic Trouble Code (DTC)
Formerly “Code”, a numerical designator used by the
SRS control unit to indicate specific SRS malfunctions.
Driver Current Source
An output of the SRS control unit which applies current
into the driver air bag assembly circuit during the
“Initiator Assembly Resistance Test”.
“Initiator Assembly Resistance Test”
Tests performed once each ignition cycle when no
malfunctions are detected during “Turn–ON” or
“Continuous Monitoring”. This test checks for the
correct SRS control unit configuration for the vehicle,
shorts to “Ignition 1” in the deployment loops, high
resistance or opens in the “Driver Side” and
“Passenger Side” circuits and measures the resistance
of the inflator assembly consisting of 1) Initiators, 2)
SRS coil assembly (driver side only), 3) Connectors
and associated wiring.
Normal Operating Voltage Range
The voltage measured between the SRS control unit
“Ignition 1” terminals and “Ground” terminals is
between 9 and 16 volts.
Passenger Current Source
An output of the SRS control unit which applies current
into the passenger air bag assembly circuit during the
“Initiator Assembly Resistance Test”.
Passenger Air Bag Assembly
An assembly located in the front of the passenger side
of the instrument panel consisting of an inflatable bag,
an inflator and an initiator.
Scan Tool
An external computer used to read diagnostic
information from on–board computers via the data link
connector.
SRS control unit
SRS control unit which provides reserve energy to the
deployment loops, deploys the air bags when required
and performs diagnostic monitoring of all SRS
components.
Serial Data
Information representing the status of the SRS.
SRS
Supplemental Restraint System.
SRS Coil Assembly
An assembly of two current–carrying coils in the driver
deployment loop that allows the rotation of the steering
wheel while maintaining the continuous contact of the
driver deployment loop to the driver air bag assembly.
SRS Wiring Harness
The wires and connectors that electrically connect the
components in the SRS.
“Turn–ON”
Test which the SRS control unit performs on the SRS
once during each ignition cycle immediately after
“Ignition 1” voltage is applied to the SRS control unit
and before “Continuous Monitoring”.

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.

SUPPLEMENTAL RESTRAINT SYSTEM 9A-27

Service Precautions for SRS
Component Service
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 number
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.
WARNING: WHEN PERFORMING SERVICE ON O
R
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 “OFF” and turn the steering
wheel so that the vehicle's wheels are pointing straight
ahead.
1. Remove SRS fuse “SRS” from left dash side lowe
r
fuse block or 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 section.
4. Disconnect passenger air bag assembly yello
w
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
Turn ignition switch to “LOCK” and remove key.
1. Connect yellow connector passenger air bag
assembly.
2. Install glove box assembly. Refer to “Passenge
r
Air Bag Assembly Replacement” in this section.
3. Connect yellow connector at the base of the
steering column.
4. Install “AIR BAG” fuse “SRS” to left dash side
lower fuse block or 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
section.

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 SRS control unit
pointing toward the front of the vehicle. It is ver
y
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 replacements.

Inspections Required After An Accident
CAUTION: Certain SRS components must be
replaced after a frontal crash involving air bag
deployment.
In all types of accidents regardless of “Air Bag”
deployment, visually inspect all of the following
components and replace as required: