Isuzu Trooper (1998-2002 year). Manual - part 1080

SUPPLEMENTAL RESTRAINT SYSTEM

9J–7

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.

431RW019

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.

740RT015

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 SDM will cause the “AIR BAG” warning lamp to turn
on 3.5 seconds and then go “OFF” whenever the ignition
switch transitions to the ON position from any other
ignition switch position and no malfunctions are detected.

“Continuous Monitoring”
Tests performed by the SDM on the SRS every 100
milliseconds while “Ignition 1” voltage is in the normal
operating voltage range at the SDM.

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
SDM to indicate specific SRS malfunctions.

Driver Current Source
An output of the SDM 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 Only Memory.
Memory which retains its contents when power is
removed from the SDM.

Ignition Cycle
The voltage at the SDM “Ignition 1” inputs, with ignition
switch “ON”, is within the normal operating voltage range
for at least ten seconds before turning ignition switch
“OFF”.

Ignition 1
A battery voltage (B+) circuit which is only powered with
the ignition switch in the ON, or START positions.

Initiator
The electrical component inside the air bag assembly
which, when sufficient current flows, sets off the chemical
reaction that inflates the air bag.

“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
SDM configuration for the vehicle, shorts to “Ignition 1” in

SUPPLEMENTAL RESTRAINT SYSTEM

9J–8

the deployment loops, high resistance or opens in the
“Driver Side High”, “Driver Side Low”, “Passenger Side
High” and “Passenger Side Low” 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 SDM “Ignition 1”
terminals and “Ground” terminals is between 9 and 16
volts.

Passenger Current Source
An output of the SDM 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 right 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.

SDM
Sensing and Diagnostic Module 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 SDM performs on the SRS once during
each ignition cycle immediately after “Ignition 1” voltage
is applied to the SDM and before “Continuous
Monitoring”.

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. 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 memory 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 SDM “Serial Data” line
terminal “24” to the data link connector terminal “9”.

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

9J–9

SRS Connector Body Face Views

D09RW016

Legend

(1) SDM
(2) Driver Air Bag Assembly
(3) Passenger Air Bag Assembly
(4) “Air Bag” Warning Lamp
(5) SRS Coil Assembly
(6) DLC
(7) Connector between Chassis Harness and

Pretensioner Harness for Driver Seat Belt (If so
equipped)

(8) Connector between Chassis Harness and

Pretensioner Harness for Passenger Seat Belt
(If so equipped)

(9) Connector between Pretensioner Harness and

driver side Pretensioner Seat Belt (If so
equipped)

(10) Connector between Pretensioner Harness and

passenger side Pretensioner Seat Belt (If so
equipped)

Repairs And Inspections Required
After An Accident

NOTE: If any SRS components are damaged, they must
be replaced.  If SRS component mounting points are
damaged, they must be replaced.

D

Never use SRS parts from another vehicle.  This does
not include remanufactured parts purchased from an
authorized dealer; they may be used for SRS repairs.

D

Do not attempt to service the SDM, the SRS coil
assembly, or the air bag assembly.  Service of these
items is by replacement only.

D

Verify the part number of replacement air bag
assembly.

CAUTION: Never use the air bag assembly from
another vehicle.  Use only the air bag assembly for
Trooper.

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 SDM, air
bag assembly and dimensional inspection of the
steering column.  Any visible damage to the SDM
mounting bracket (s) requires replacement, and the
steering column must be dimensionally inspected,
whether deployment occurred or not.

SUPPLEMENTAL RESTRAINT SYSTEM

9J–10

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:

D

Air bag assembly

D

SDM

CAUTION: Refer to “SDM Replacement Guidelines”
below for important information on SDM
replacement in both deployment and non
deployment crashes.

D

SRS coil assembly — Inspect wiring and connector
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:

D

Steering column — Refer to Inspection Required
“After an Accident” in this manual.

D

Knee bolsters and mounting points — Inspect for any
distortion, bending, cracking, or other damage.

D

I/P steering column reinforcement plate — Inspect for
any distortion, bending, cracking, or other damage.

D

I/P braces — Inspect for any distortion, bending,
cracking, or other damage.

D

Seat belts and mounting points — Refer to “Seat
Belts” in Section “Seat Belt” of this workshop manual.

SDM Replacement Guidelines

SDM replacement policy requires replacement of SDM,
after crash involving air bag deployment when “SRS
Warning Lamp” turn “ON”, “SRS Diagnosis” should be
done according to Section “Restraint Control System.”
If accident without deployment air bag, it is not necessary
replacement of SDM when do not indicate to replace the
SDM by scan tool after SRS system check.

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.

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 SDM 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 SDM is
removed.
Many of the service procedures require removal of the
“C–21” 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 C–21, from left dash side lower

fuse block or disconnect battery.

2. Disconnect yellow 2–pin connector at the base of

steering column. 

3. Remove glove box assembly, refer to “Passenger Air

Bag Assembly Replacement” in this manual.

4. Disconnect yellow 2–pin connector behind the glove

box assembly.

CAUTION: With the “C–21” 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.  Use only the air bag assembly for
Trooper.
Turn ignition switch to “LOCK” and remove key.

1. Connect yellow 2–pin connector passenger air bag

assembly.

2. Install glove box assembly. Refer to “Passenger air

bag assembly replacement” in this manual.

3. Connect yellow 2–pin connector at the base of

steering column.

4. Install “AIR BAG” fuse C–21 to left dash side lower

fuse block or connect battery.

Turn ignition switch to “ON” and verify that the “AIR BAG”
warning lamp turn on 3.5 seconds and then turns “OFF.” If
it does not operate as described, perform the “SRS
Diagnostic System Check” in this manual.