2004 ISUZU TF SERIES tow

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-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:

9A-30 SUPPLEMENTAL RESTRAINT SYSTEM

SRS Control Unit
5. Remove the three SRS control unit fixing bolts and
remove SRS control unit.


RTW49JSH000101
Legent
(1) SRS control unit
(2) SRS Harness
(3) Connector Position Assurance

Service Precautions
WARNING: DURING SERVICE PROCEDURES, BE
VERY CAREFUL WHEN HANDLING SRS control
unit. NEVER STRIKE OR JAR SRS control unit.
UNDER SOME CIRCUMSTANCES, IT COULD
CAUSE DEPLOYMENT AND RESULT IN
PERSONAL INJURY OR IMPROPER OPERATION
OF THE SUPPLEMENTAL RESTRAINT SYSTEM
(SRS) . SRS control unit MOUNTING BRACKET
BOLTS MUST BE CAREFULLY TORQUED TO
ASSURE PROPER OPERATION. NEVER POWE
R
UP THE SRS WHEN SRS control unit IS NOT
RIGIDLY ATTACHED TO THE VEHICLE. 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.
WARNING: PROPER OPERATION OF THE SRS
CONTROL UNIT REQUIRES THE SRS CONTROL
UNIT TO BE RIGIDLY ATTACHED TO THE
VEHICLE STRUCTURE AND THAT THE ARROW
ON THE SENSOR BE POINTING TOWARD THE
FRONT OF THE VEHICLE.
SRS control unit is specifically calibrated and is keyed
to the SRS control unit location SRS wiring harness.
Caution should be used to ensure proper location of
the SRS control unit. The keying of the SRS control
unit to its location and wiring harness connectors
should never be modified in the field.

Removal
1. Disable the SRS (Refer to “Disabling the SRS” in
this section).
2. Remove the transmission knob (for M/T) and
transfer lever knob.
3. Remove the front console assembly and
disconnect wiring harness connector.
4. Pull CPA (Connector Position Assurance) out and
push connector lock down to disconnect the SRS
control unit harness connector.

Installation
1. Install the SRS control unit on bracket and fixing
bolts and tighten the fixing bolts to the specified
torque.
Torque: 7




2 N
 m (0.7




0.2 kg
 m/61 lb in)
2. Connect the SRS control unit harness connecto
r
and after that, put CPA into connector.
3. Install the front console.
4. Install the transmission knob (for M/T) and transfe
r
lever knob.

RESTRAINT CONTROL 9A1-11

3.
When all circuitry outside the SRS control unit has
been found to operate properly, as indicated by the
appropriate diagnostic chart, then and only then
should the SRS control unit be replaced.


Chart A SRS control unit Integrity Check
WARNING: DURING SERVICE PROCEDURES. BE VERY CAREFUL WHEN HANDLING A SRS CONTROL
UNIT. NEVER STRIKE OR JAR THE SRS CONTROL 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 POINTING 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

Step Action Yes No
1

1. This chart assumes that the “SRS Diagnostic System
Check” and either a symptom chart or a diagnostic trouble
code chart diagnosis have been performed. When all
circuitry outside the SRS control unit has been found to
operate properly, as indicated by the appropriate diagnostic
chart, and the symptom or DTC remains current, the
following

2. Diagnostic procedures must be performed to verify the need
for SRS control unit replacement.

3. Ignition switch “OFF”.
4. Reconnect all SRS components, ensure all components are
properly mounted.

5. Ensure the ignition switch has been “OFF” for at least 15
seconds.

6. Note “AIR BAG” warning lamp as ignition switch is turned
“ON.”
Does warning lamp flash 7 times then go “OFF”? The symptom or
DTC is no longer
occurring.
Clear SRS
diagnostic trouble
codes.
Repeat “SRS
Diagnostic System
Check” Go to Step 2
2 Using a scan tool request diagnostic trouble code display.
Is the same symptom or DTC occurring as was when the “SRS
Diagnostic System Check” was first performed? Go to Step 3 Ignition switch
“OFF”.
Go to the
appropriate chart for
the indicated
malfunction.
3
1. Clear “SRS Diagnostic Trouble Codes”.

2. Ignition switch “OFF” for at least two minutes.

3. Note “AIR BAG” warning lamp as ignition switch is turned
“ON.”
Does warning lamp flash 7 times then go “OFF”? SRS is functional
and free of
malfunctions.
No further diagnosis
is required.
Go to Step 4 Ignition switch
“OFF”.
Replace SRS control
unit.
Go to Step 4
4 Reconnect all SRS components, ensure all components are
properly mounted.
Was this step finished? Repeat the “SRS
Diagnostic System
Check” Go to Step 4

9A1-38 RESTRAINT CONTROL SYSTEM

DTC B0051 (Flash Code 51) Squib Circuit Activated (Crash Deteted)
WARNING: DURING SERVICE PROCEDURES. BE VERY CAREFUL WHEN HANDLING A SRS CONROL UNIT.
NEVER STRIKE OR JAR THE SRS CONTROL 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 POINTING TOWARD THE
FRONT OF THE VEHICLE TO ENSURE PROPER OPERATION OF THE SRS. THE SRS CONTROL UNIT CAUSE
DEPLOYMENT AND RESULT IN PERSONAL INJURY.


Step Action Yes No
1 Was the “SRS Diagnostic System Check” performed? Go to Step 2. Go to the “SRS
Diagnostic System
Check”
2 Ignition switch “OFF.”
Have air bag assemblies deployed? Replace
components and
perform
inspections as
directed in
“repairs and
inspections
required after an
accident” in this
section.
clear diagnostic
trouble codes.
Repeat “SRS
Diagnostic System
Check” Go to Step 3
3 Inspect front of vehicle and undercarriage for sings of impact.
Were signs of impact found? Replace
components and
perform
inspections as
directed in
“Repairs and
Inspections
Required After An
Accident” in this
section.
Clear diagnostic
trouble codes.
Repeat “SRS
Diagnostic System
Check” Ignition switch
“OFF”.
Replace SRS
control unit.
Reconnect all SRS
system
components,
ensure all
components are
properly mounted.
Repeat “SRS
Diagnostic System
Check”

9A1-40 RESTRAINT CONTROL SYSTEM

DTC Chart Test Description
Number(s) below refer to step number(s) on the
diagnostic chart:
2.
If air bag assembly have not deployed, DTC B0053
may have falsely set.
3.
If DTC B0053 has set with no signs of frontal impact,
the diagnostic trouble code has falsely set.


DTC B0053 (Flash Code 53) Deployment Command Despite Present Trouble Code
WARNING: DURING SERVICE PROCEDURES. BE VERY CAREFUL WHEN HANDLING A SRS CONTROL
UNIT. NEVER STRIKE OR JAR THE SRS CONTROL 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 POINTING 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.


Step Action Yes No
1 Was the “SRS Diagnostic System Check” performed? Go to Step 2 Go to the “SRS
Diagnostic System
Check”
2 Ignition switch “OFF.”
Have air bag assembles deployed? Replace
components and
perform
inspections as
directed in
“Repairs And
Inspections
Required After An
Accident” in this
section.
Clear diagnostic
trouble codes.
Repeat the “SRS
Diagnostic System
Check” Go to Step 3
3 Inspect front of vehicle and undercarriage for signs of impact.
Were signs of impact found? Replace
components and
perform
inspections as
directed in
“Repairs And
Inspections
Required After An
Accident” in this
section.
Clear diagnostic
trouble codes.
Repeat “SRS
Diagnostic System
Check” Ignition switch
“OFF.”
Replace SRS
control unit.
Reconnect all SRS
system
components,
ensure all
components are
properly mounted.
Repeat the “SRS
Diagnostic System
Check”

9A1-62 RESTRAINT CONTROL SYSTEM

DTC B1000 (Flash Code 72) SDM Internal Fault (SDM=SRS control unit)
WARNING: DURING SERVICE PROCEDURES. BE VERY CAREFUL WHEN HANDLING A SRS CONTROL
UNIT. NEVER STRIKE OR JAR THE SRS CONTROL 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 POINTING 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.
CAUTION: If DTC B1000 can not clear by Tech2, it is necessary to replace the SRS control unit.

Step Action Yes No
1 Was the “SRS Diagnostic System Check” performed? Ignition switch
“OFF.”
Replace SRS
control unit.
Repeat the “SRS
Diagnostic System
Check” Go to the “SRS
Diagnostic System
Check”