ISUZU TF SERIES 2004 Workshop Manual

RESTRAINT CONTROL 9A1-31

Step Action Yes No
6 Measure resistance on SRS control unit harness connector from
terminal “45” to terminal “35” (ignition).
Does 5-8840-0285-0 display “OL” (infinite)? Go to Step 7
Replace SRS
harness.
Go to Step 9
7 Measure resistance on SRS control unit harness connector from
terminal “46” to terminal “35” (ignition).
Does 5-8840-0285-0 display “OL” (infinite)? Go to Chart A
Replace SRS
harness.
Go to Step 9
8

1. Ignition switch “OFF.”

2. Disconnect SRS driver / passenger load tool 5-8840-2421-0
from SRS coil assembly harness connector.

3. Connect SRS driver / passenger load tool 5-8840-2421-0 and
appropriate adapter to driver air bag assembly harness
connector. located top of the steering column connector.

4. Reconnect SRS coil assembly harness connector as the base
of steering column.

5. Ignition switch “ON.”
Is DTC B0024 current? Ignition switch
“OFF.”
Replace SRS coil
assembly.
Go to Step 9 Ignition switch
“OFF.”
Replace driver air
bag assembly.
Go to Step 9
9

1. Reconnect all components ensure all component are properly
mounted.

2. Clear diagnostic trouble codes.
Was this step finished? Go to the “SRS
Diagnostic System
Check” Go to Step 9

9A1-32 RESTRAINT CONTROL SYSTEM

DTC B0026 (Flash Code 26) Driver Airbag Squib Circuit High Resistance


RTW49JLF000101

Circuit Description
When the ignition switch is turned “ON”, the SRS
control unit will perform tests to diagnose critical
malfunctions within itself. Upon passing these tests,
“Ignition 1”, and deployment loop voltages are
measured to ensure they are within their respective
normal voltage ranges.
The SRS control unit then proceeds with the
“Resistance Measurement Test” “Driver Bag Low”
terminal “46” is grounded through a current sink and the
driver current source connected to “Driver Bag High”
terminal “45” allows a known amount of current to flow.
By monitoring the voltage difference between “Drive
r
Bag High” and “Driver Bag Low”, the SRS control unit
calculates the combined resistance of the driver air bag
assembly, SRS coil assembly, harness wiring circuits
“Driver Bag High” and “Driver Bag Low” and connecto
r
terminal contact.

RESTRAINT CONTROL 9A1-33

DTC Will Set When
The combined resistance of the driver air bag
assembly, SRS Coil assembly, harness wiring circuits
“Driver Bag High” and “Driver Bag Low”, and connector
terminal contact is above a specified value. This test
run once each ignition cycle during the “Resistance
Measurement Test” when:
1.
No “higher priority faults” are detected during “Turn–
ON”
2.
“Ignition 1” voltage is in the specified value.

Action Taken
SRS control unit turns “ON” the “AIR BAG” warning
lamp and sets DTC B0026.

DTC Will Clear When
The ignition switch is turned “OFF”.



DTC Chart Test Description
Number(s) below refer to step number(s) on the
diagnostic chart:
2.
This test determines whether the malfunction is in
the SRS control unit.
3.
This test verifies proper connection of the yellow
connector at the base of the steering column.
4.
This test checks for proper contact and/or corrosion
of the connector terminals at the base of steering
column.
5.
This test isolate the malfunction to one side of the
SRS coil assembly yellow connector located at the
base of the steering column.
6.
This test determines whether the malfunction is due
to high resistance in the wiring.
7.
This test determines whether the malfunction is in
the SRS coil assembly or the driver air bag
assembly.

Diagnostic Aids
An intermittent condition is likely to be caused by a poor
connection at terminals “1” and “2” of the SRS coil
connector at the base of the steering column, terminal
“1” and “2” of the driver air bag assembly connector at
the top of the steering column, SRS control unit
terminals “45” and “46” or a poor wire to terminal
connection in circuit “Driver Bag High” or “Driver Bag
Low” The test for this diagnostic trouble code is onl
y
run while the “AIR BAG” warning lamp is performing
the bulb check. When a scan tool “Clear Codes”
command is issued and the malfunction is still present,
the DTC will not reappear until the next ignition cycle.

DTC B0026 (Flash Code 26) Driver Airbag Squib Circuit High Resistance

Step Action Yes No
1 Perform the “SRS Diagnostic System Check”.
Was the “SRS Diagnostic System Check” performed? Go to Step 2 Repeat the “SRS
Diagnostic System
Check”
2

1. Check the driver air bag squib circuit for open.

2. If the problem found, repair as necessary.
Was a problem found? Verify repair Go to Step 3
3

1. Ignition switch “OFF.”

2. Disconnect SRS coil assembly yellow connector located at
base of steering column is seated properly.
Is the connector connected properly? Go to Step 4 Seat SRS coil
assembly
connector
properly.
Go to Step 8

9A1-34 RESTRAINT CONTROL SYSTEM

Step Action Yes No
4

1. Disconnect and inspect the SRS coil assembly yellow
connector located base of steering column.

2. If ok, reconnect the SRS coil assembly yellow connector.
3. Ignition switch “ON.”
Is DTC B0026 current? Go to Step 5 Go to Step 8
5

1. Ignition switch “OFF.”

2. Disconnect SRS coil and passenger air bag assembly, yellow
2–pin connector located at the base of steering column and
behind the glove box assembly.

3. Connect SRS driver / passenger load tool 5-8840-2421-0 and
appropriate adapter to SRS coil and passenger air bag
assembly harness connectors.

4. Ignition switch “ON.”
Is DTC B0026 current? Go to Step 6 Go to Step 7
6

1. Ignition switch “Off. “

2. There has been a increase in the total circuit resistance of
the driver deployment loop.

3. Use the high resolution ohmmeter mode of the DVM while
checking circuits “Driver Bag High” and “Driver Bag Low”,
and SRS control unit connector terminal “45” and “46” to
locate the root cause.
Was a fault found? Replace SRS
harness.
Go to Step 8 Go to Chart A
7

1. Ignition switch “OFF.”

2. Disconnect SRS driver / passenger load tool from SRS coil
assembly harness connector.
3. Connect SRS driver / passenger load tool 5-8840-2421-0 on
the top of steering column.

4. Reconnect SRS coil assembly harness connector as the base
of steering column.

5. Ignition switch “ON.”
Is DTC B0026 current? Ignition switch
“OFF.”
Replace SRS coil
assembly.
Go to Step 8 Ignition switch
“OFF.”
Replace driver air
bag assembly.
Go to Step 8
8

1. Reconnect all components ensure all component are
properly mounted.

2. Clear diagnostic trouble codes.
Was this step finished? Repeat the “SRS
Diagnostic System
Check” Go to Step 8

RESTRAINT CONTROL 9A1-35

DTC B0033 (Flash Code33) ECU Connector Poor Connection


RTW49JLF000101

Circuit Description
The connector of SRS control unit is connected
completely. ECPA(Electrical Connector Position
Assurance) circuit is closed after that.
SRS control unit supervises it by self-diagnosis.

DTC Will Set When
ECPA circuit is open.
Action Taken
Connect completely the SRS control unit.

DTC Will Clear When
The ignition switch is turned “OFF”.

9A1-36 RESTRAINT CONTROL SYSTEM

DTC (Flash Code33) B0033 ECU Connector Poor Connection

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”
Reconnect the ECPA on SRS control unit connector yellow 52-
pin connector located at the base of instrument panel center.
Ignition switch “ON”
Is DTC B0033 current? Go to Step 3 Reconnect the
ECPA properly.
Go to Step2
3 Clear Diagnostic trouble codes.
Is the action complete? Go to “SRS
Diagnostic System
Check” Go to Step 3

RESTRAINT CONTROL 9A1-37

DTC B0051 (Flash Code 51) Squib Circuit Activated (Crash Detected)


RTW49JLF000101

Circuit Description
The SRS control unit contains a sensor which converts
vehicle velocity changes 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 ai
r
bags and causing DTC B0051 to set.

DTC Will Set When
The SRS control unit detects a frontal crash, up to 30
degrees off the centerline of the vehicle, of sufficient
force to warrant deployment of the air bags.

Action Taken
SRS control unit turns “ON” the “AIR BAG” warning
lamp records “Crash Data”, and sets a diagnostic
trouble code.

DTC Will Clear When
The SRS control unit is replaced.

DTC Chart Test Description
Number(s) below refer to step number(s) on the
diagnostic chart:
2.
If air bag assembly(s) has not deployed, DTC B0051
may have falsely set.
3.
If DTC B0051 has set with no signs of frontal impact,
the diagnostic trouble code has falsely set.

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”

RESTRAINT CONTROL 9A1-39

DTC B0053 (Flash Code 53) Deployment Command Despite Present Trouble
Code


RTW49JLF000101

Circuit Description
The SRS control unit contains a sensor which converts
vehicle velocity changes 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 ai
r
bags. DTC B0053 is set accompanying with DTC
B0051 when a deployment occurs while an air bag
assembly circuit fault is present that could possible
result in a no deployment situation in one or both air bag
assemblies.


DTC Will Set When
The SRS control unit detects a frontal crash, up to 30
degrees off the centerline of the vehicle, of sufficient
force to warrant deployment of the air bags and an
inflator circuit fault is present.

Action Taken
SRS control unit turns “ON” the “AIR BAG” warning
lamp records “Crash Data”, and sets a diagnostic
trouble code.

DTC Will Clear When
The SRS control unit is replaced.

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”