Page 5649 of 6020

9A-14 SUPPLEMENTAL RESTRAINT SYSTEM
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 30–Volt Loop Reserve (30VLR) energy supply to
provide deployment energy when ignition voltage is
lost in a frontal crash.
2. Frontal Crash Detection — The SRS control unit monitors vehicle velocity changes to detect frontal
crashes which are severe enough to warrant
deployment.
3. Air Bag Deployment — W hen a frontal crash o
f
sufficient force is detected, the SRS control unit
will cause enough current to flow through the ai
r
bag assembly to deploy the air bag.
4. Malfunction Detection — The SRS control unit 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 unit records information regarding SRS status during
frontal crash.
6. Malfunction Diagnosis — The SRS control unit 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 “SRS” warning lamp.
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
“SRS” warning lamp to ground when the SRS control
unit harness connector is disconnected or CP
A
(Connector Position Assurance) is not inserted even i
f
completely connected. This will cause the “SRS”
warning lamp to come “ON” steady whenever the
ignition switch is at the ON or START positions with
the SRS control unit disconnected.
RTW 79ASH000401
Legend
(1) SRS Control Unit
(2) SRS Harness
“SRS” Warning Lamp
Ignition voltage is applied to the “SRS” warning lamp
when the ignition switch is at the ON or START
positions. The SRS control unit controls the lamp b
y
providing ground with a lamp driver. The “SRS”
warning lamp is used in the SRS to do the following:
1. Verify lamp and SRS control unit operation b
y
flashing SEVEN (7) times when the ignition switch
is first turned “ON”.
2. W arn 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 “SRS “ warning lamp is the key to drive
r
notification of SRS malfunctions. For proper lamp
operation, refer to the “SRS Diagnostic System Check”
in this section.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5650 of 6020

SUPPLEMENTAL RESTRAINT SYSTEM 9A-15
RTW 79ASH000501
SRS Coil Assembly
The SRS coil assembly consists of two current
carrying coils. This is attached to the steering column
and allows rotation of the steering wheel while
maintaining continuous contact of the drive
r
deployment loop to the driver air bag assembly.
There is a shorting clip on the yellow connector nea
r
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 ai
r
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 consists of an inflatable air bag
assembly and an inflator. W hen 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 assembl
y
connector which connects the SRS coil assembly. The
shorting clip shorts across the driver air bag assembl
y
circuits when the 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.
RTW 79ASH001001
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.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5651 of 6020

9A-16 SUPPLEMENTAL RESTRAINT SYSTEM
RTW 79ASH000201
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 uppe
r
half in his seat.
RTW 49JSH000201
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 o
f
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 non-periodic 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.
W ith 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 “SRS” 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.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5652 of 6020

SUPPLEMENTAL RESTRAINT SYSTEM 9A-17
“Continuous Monitoring”
Tests are 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”.
Driver Air Bag Assembly
An assembly located in the steering wheel hub
consisting of an inflatable bag, an inflator and an
initiator.
EEPROM
Electrically Erasable Programmable Read Onl
y
Memory. Memory which retains its contents when
power is removed from the SRS control unit.
Ignition Cycle
The voltage at the SRS control unit “Ignition 1” input,
with ignition switch “ON”, is within the normal operating
voltage range for at least ten seconds before turning
the ignition switch “OFF”.
Ignition 1
A battery voltage (B+) circuit which is only powered
when the ignition switch is in the ON, or START
position.
Initiator
The electrical component inside the air bag assembl
y
which, when sufficient current flows, sets off the
chemical reaction that inflates the air bag.
“Initiator Assembly Resistance Test”
Tests are performed once for each ignition cycle when
no malfunctions are detected during “Turn–ON” o
r
“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 drive
r
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 afte
r
“Ignition 1” voltage is applied to the SRS control unit
and before “Continuous Monitoring”.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5653 of 6020

9A-18 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
NON-POWERED 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 “SRS”
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. Current
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 o
f
a scan tool such as the Tech 2 Diagnostic Computer,
SRS Driver/Passenger Load Tool 5-8840-2421-0,
Connector Test Adapter Kit 5-8840-2835-0 and the
DMM (Digital Multimeter) 5-8840-0366-0.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5654 of 6020
SUPPLEMENTAL RESTRAINT SYSTEM 9A-19
SRS Connector Body Face Views
RTW 79AMF000201
Legend
(1) SRS control unit
(2) Driver Air Bag Assembly
(3) Passenger Air Bag Assembly
(4) “SRS” W arning Lamp
(5) DLC
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5655 of 6020

9A-20 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 the replacement air bag assembly.
CAUTION: Never use the air bag assembly from
another vehicle or different model year air bag
assembly.
Use only a new air bag assembly matched 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
has been 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 the SRS control unit after a crash
involving air bag deployment when the “SRS W arning
Lamp” turned “ON”, the “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 the SRS harness. It is
replacement 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.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007
Page 5656 of 6020

SUPPLEMENTAL RESTRAINT SYSTEM 9A-21
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 UNNECESSARY SRS
REPAIRS.
The SRS control unit in Driver–Passenger SRS can
maintain sufficient voltage to cause a deployment fo
r
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 assembl
y
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 the
key.
1. Remove the SRS fuse “SRS”, from the side of the driver’s side of the instrument panel fuse block o
r
disconnect the battery.
2. Disconnect the yellow connector at the base of the steering column.
3. Remove the glove box assembly, refer to “Passenger Air Bag Assembly Replacement” in
this manual.
4. Disconnect the yellow connector behind the glove box assembly.
CAUTION: With the “SRS” fuse removed and
ignition switched “ON”, the “SRS” 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 or different model year air bag
assembly.
Use only a new air bag assembly matched to the
TFR/S which is being repaired.
Turn the ignition switch to “LOCK” and remove the
key.
1. Connect the yellow connector passenger air bag assembly.
2. Install the glove box assembly. Refer to “Passenger air bag assembly replacement” in this
manual.
3. Connect the yellow connector at the base of the steering column.
4. Install the “AIR BAG” fuse “SRS” to the side of the driver’s side of the instrument panel fuse block o
r
connect the battery.
Turn the ignition switch to “ON” and verify that the
“SRS” warning lamp flashes seven times and then
turns to “LOCK”. If it does not operate as described,
perform the “SRS Diagnostic System Check” in this
manual.
Handling / Installation / Diagnosis
1. The air bag assembly should not be subjected to temperatures above 65
°C (150°F).
2. The 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. W hen the 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 “SRS”
warning lamp operation and will lead you to the
correct chart to diagnose any SRS malfunctions.
Bypassing these procedures may result in
extended diagnostic time, incorrect diagnosis, and
incorrect parts replacement.
BACK TO CHAPTER INDEX TO MODEL INDEXISUZU KB P190 2007