ISUZU TROOPER 1998 Service Repair Manual

RESTRAINT CONTROL SYSTEM 9J1±4
System Schematic
D09RW014
SRS Diagnostic System Check
The diagnostic procedures used in this section are
designed to find and repair SRS malfunctions. To get the
best results, it is important to use the diagnostic charts
and follow the sequence listed below:
A. Perform the ªSRS Diagnostic System Check.º
The ªSRS Diagnostic System Checkº must be the
starting point of any SRS diagnostics. The ªSRS
Diagnostic System Checkº checks for proper ªAIR
BAGº warning lamp operation, the ability of the SDM
to communicate through the ªSerial Dataº line and
whether SRS diagnostic trouble codes exist.
B. Refer to the proper diagnostic chart as directed by the
ªSRS Diagnostic System Check.º
The ªSRS Diagnostic System Checkº 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.
C. Repeat the ªSRS Diagnostic System Checkº after any
repair or diagnostic procedures have been
preformed.
Performing the ªSRS Diagnostic System Checkº after
all repair or diagnostic procedures will ensure that the
repair has been made correctly and that no other
malfunctions exist
Circuit Description
When the ignition switch is first turned ªONº, ªIgnition 1º
voltage is applied from the ªC±21º fuse to the SDM at the
ªIgnition 1º input terminals ª12º. The SDM responds by
flashing the ªAIR BAGº warning lamp turn on 3.5 seconds,
while performing tests on the SRS.
Notes On System Check Chart:
1. The ªAIR BAGº warning lamp should turn on 3.5
seconds after ignition is first turned ªONº.
2. After the ªAIR BAGº warning lamp turn on 3.5
seconds, it should turn ªOFFº
3. This test checks for the proper operation of the
ªSerial Dataº line. This test will also determine
whether history diagnostic trouble codes are stored
and, if so, identify them.
4. Improper operation of the ªAIR BAGº warning lamp
is indicated. This test differentiates a warning lamp
stays ªONº condition from a warning lamp does not
come ªONº condition.
5. This test checks for proper operation of the ªSerial
Dataº line. This test will also identify the stored
diagnostic trouble codes and whether they are
current or history.
Diagnostic Aids:
The order in which diagnostic trouble codes are
diagnosed is very important. Failure to diagnose the

9J1±5
RESTRAINT CONTROL SYSTEM
diagnostic trouble codes in the order specified may result in extended diagnostic time, incorrect diagnosis and
incorrect parts replacement.
SRS Diagnostic System Check
StepActionYe sNo
1Note the ªAir Bagº warning lamp as ignition switch is turned ªON.º
Does the ªAIR BAGº warning lamp turn on 3.5 seconds?
Go to Step 2Go to Step 3
2Note the ªAIR BAGº warning lamp after it turn on 3.5 seconds.
Does the ªAIR BAGº warning lamp go ªOFFº?
Go to Step 4Go to Step 5
3Note the ªAIR BAGº warning lamp as ignition switch is turned
ªONº.
Does the ªAIR BAGº warning lamp come ªONº steady?
Go to Chart BGo to Chart C
41. Note the ªAIR BAGº warning lamp as that ignition switch is
turned ªON.º
Ignition switch ªOFF.º
2. Connect a scan tool to data link connector.
3. Follow direction given in the scan tool instruction manual.
Ignition switch ªON.º
4. Request the SRS diagnostic trouble code display, recode all
history diagnostic trouble code(s). specify as such, on repair
order
Is (are) diagnostic trouble code(s) displayed?Ignition switch
ªOFFº
When DTC 71 is
set, go to DTC 71
Chart
For all other
history codes
refer to
ªDiagnostic Aidsº
For that specific
DTC
A history DTC
indicates the
malfunction has
been repaired or
is intermittent
SRS is functional
and free of
malfuncitons, no
further diagnosis
is required
If scan tool
indicated ªNO
DATA
RECEIVED,º
refer to chassis
electrical section8
51. Ignition switch ªOFF.º
2. Connect a scan tool to data link connector.
3. Follow directions as given in the scan tool instruction manual.
4. Ignition switch ªON.º
5. Request the SRS diagnostic trouble code display, Recode all
diagnostic trouble code(s), specifying as current or history on
repair order.
Is (are) diagnostic trouble code (s) displayed?Ignition switch
ªOFFº
When DTC 53 is
set, go to DTC 53
chart
When DTC 51 is
set, go to DTC 51
chart
When DTC 19 is
set, go to DTC 19
chart
When DTC 25 is
set, go to DTC 25
chart
Diagnose
remaining current
DTCs from
lowest to highest
When only history
DTCs exist, refer
to ªDiagnostics
Aidsº for that
specific DTC
A history DTC
indicates the
malfunction has
been repaired or
is intermittent
If scan tool
indicates ªNo
Data Received,º
refer to chassis
electrical section8

RESTRAINT CONTROL SYSTEM 9J1±6
Chart A SDM Integrity Check
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Circuit Description:
When the SDM recognizes ªIgnition 1º voltage, applied to
terminals ª12º, is greater than 9 volts, the ªAIR BAGº
warning lamp is turned on 3.5 seconds to verify operation.
At this time the SDM performs ªTurn±ONº tests followed
by ªContinuous Monitoringº tests. When a malfunction is
detected, the SDM sets a current diagnostic trouble code
and illuminates the ªAIR BAGº warning lamp. The SDM
will clear current diagnostic trouble codes and move them
to a history file when the malfunction is no longer detected
and/or the ignition switch is cycled, except for DTCs 19,
25, 51, 53 and 71. DTC 71 can only be cleared using a
scan tool ªClear Codesº command. If DTCs 51, 53 are not
indicated then DTC 71 is not existing. DTCs 51, 53 and 71
can not be cleared after a ªClear Codesº command is
issued.
Chart Test Description:
Number(s) below refer to step number(s) on the
diagnostic chart:
1. This test confirms a current malfunction. If no
current malfunction is occurring (history DTC set)
the ªDiagnostic Aidsº for the appropriate diagnostic
trouble code should be referenced. The SDM
should not be replaced for a history diagnostic
trouble code.
2. This test checks for a malfunction introduced into the
SRS during the diagnostic process. It is extremely
unlikely that a malfunctioning SDM would cause a
new malfunction to occur during the diagnostic
process.
3. When all circuitry outside the SDM has been found
to operate properly, as indicated by the appropriate
diagnostic chart, then and only then should the SDM
be replaced.

9J1±7
RESTRAINT CONTROL SYSTEM
Chart A SDM Integrity Check
WARNING: DURING SERVICE PROCEDURES. BE VERY CAREFUL WHEN HANDLING A SENSING AND
DIAGNOSTIC MODULE (SDM). NEVER STRIKE OR JAR THE SDM. NEVER POWER UP THE SRS WHEN THE
SDM IS NOT RIGIDLY ATTACHED TO THE VEHICLE. ALL SDM 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 SDM COULD BE ACTIVATED WHEN POWERED WHILE
NOT RIGIDLY ATTACHED TO THE VEHICLE WHICH COULD CAUSE DEPLOYMENT AND RESULT IN
PERSONAL INJURY.
Step
ActionYe sNo
11. This chart assumes that the ªSRS Diagnostic System Checkº
and either a symptom chart or a diagnostic trouble code chart
diagnosis have been performed. When all circuitry outside the
SDM 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 SDM replacement.
3. Ignition switch ªOFFº.
4. Reconnect all SRS components, ensure all components are
properly mounted.
5. Ensure the ignition switch has been ªOFFº for at least 15
seconds.
6. Note ªAIR BAGº warning lamp as ignition switch is turned
ªON.º
Does warning lamp turn on 3.5 seconds then go ªOFFº?
The symptom or
DTC is no longer
occurring
Clear SRS
diagnostic trouble
codes
Repeat ªSRS
Diagnostic
System Checkº
Go to Step 2
2Using a scan tool request diagnostic trouble code display
Is the same symptom or DTC occurring as was when the ªSRS
Diagnostic System Check º was first performed?
Go to Step 3
Ignition switch
ªOFFº
Go to the
appropriate chart
for the indicated
malfunction
31. Clear ªSRS Diagnostic Trouble Codesº.
2. Ignition switch ªOFFº for at least two minutes.
3. Note ªAIR BAGº warning lamp as ignition switch is turned
ªON.º
Does warning lamp turn on 3.5 seconds then go ªOFFº?SRS is functional
and free of
malfunctions
No further
diagnosis is
required
Go to Step 4
Ignition switch
ªOFFº
Replace SDM
Go to Step 4
4Reconnect all SRS components, ensure all components are
properly mounted.
Was this step finished?Repeat the ªSRS
Diagnostic
System Checkº
Go to Step 4

RESTRAINT CONTROL SYSTEM 9J1±8
Chart B ªAIR BAGº Warning Lamp Comes ªONº Steady
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Circuit Description:
When the ignition switch is first turned ªONº, ªIgnition 1º
voltage is applied from the ªC±10º fuse to ªAIR BAGº,
warning lamp which is connected to ªSRS Warning
Lampº, terminal ª7º. The ªC±21º fuses apply system
voltage to the ªIgnition 1º inputs, terminals ª12º. The SDM
responds by turning on the ªAIR BAGº warning lamp 3.5
seconds. If ªIgnition 1º is less than 9 volts, the ªAIR BAGº
warning lamp will come ªONº solid with no DTCs set.
Chart Test Description:
Number(s) below refer to step number(s) on the
diagnostic chart.
2. This test checks for an open in the ªIgnition 1º circuit
to the SDM.
3. This test checks for the voltage of ªIGNITION 1º.
4. This test determines whether the malfunction is a
short to ground in IB04±WHT/RED.

9J1±9
RESTRAINT CONTROL SYSTEM
Chart B ªAIR BAGº warning lamp comes ªONº Steady
StepActionYe sNo
11. When measurements are requested in this chart use
5±8840±0285±0 DVM with correct terminal adapter from
5±8840±0385±0.
2. Ignition switch ªOFF.º
3. Connect scan tool to data link connector, follow directions as
given in the scan tool instruction MANUAL.
4. Ignition switch ªON.º
5. Request SRS diagnostic trouble code display.
Dose scan tool indicate ªNo Data Receivedº?
Go to Step 2Go to Step 3
21. Ignition switch ªOFFº.
2. Inspect SDM harness connector connection to SDM.
Is it securely connected to the SDM?
Ignition switch
ªOFFº
Replace SDM
Go to Step 5
Connect SDM
securely to
de±activate
shorting clip in
SDM harness
connector
Go to Step 5
3Using scan tool, request SRS data list.
Is ªignitionº less than 9 volts?
Go to Step 4
Ignition switch
ªOFFº
Replace SDM
Go to Step 5
41. Ignition switch ªOFF.º
2. Disconnect SRS coil and passenger air bag assemblies.
yellow 2±pin connector located at base of steering column and
behind the glove box assembly.
Disconnect SDM.
3. Disconnect the connector of ªSRS Warning Lampº of
instrument cluster.
4. Measure resistance from SDM harness connector terminal ª7º
to ground ª6º.
Does 5±8840±0285±0 display ªOLº (Infinite)?
Go to Chart A
Replace SRS
harness
Go to Step 5
5Reconnect all SRS components, ensure all components are
properly mounted.
Was this step finished?Repeat the ªSRS
Diagnostic
System Checkº
Go to Step 5

RESTRAINT CONTROL SYSTEM 9J1±10
Chart C ªAIR BAGº Warning Lamp Does Not Come ªONº Steady
D09RW014
Circuit Description:
When the ignition switch is first turned ªONº, ªIgnition 1º
voltage is applied from the ªC±10º fuse to the ªAIR BAGº
warning lamp which is connected to ªSRS Warning
Lampº, terminal ª7º. The ªC±21º fuse apply system
voltage to the ªIgnition 1º inputs, terminals ª12º. The SDM
responds by turning on the ªAIR BAGº warning lamp 3.5
seconds. If ªIgnition 1º is more than 16 volts, the ªAIR
BAGº warning lamp will be still ªOFFº solid with no DTCs
set.
Chart Test description:
Number(s) below refer to step number(s) on the
diagnostic chart:
1. This test decides whether power is available to SDM
warning lamp power feed circuit.2. This test determines whether the voltage is present
in the warning lamp circuit.
3. This test determines if the malfunction is in the
instrument cluster.
4. This test checks for open in the warning lamp
circuitry.
5. This test isolates the IB04±WHT/RED circuit and
checks for a short in the IB04±WHT/RED circuit to
B+.
8. This test checks for a short from the SDM warning
lamppower feed circuit to ground.
9. This test determines whether the short to ground is
due to a short in the wiring.

9J1±11
RESTRAINT CONTROL SYSTEM
Chart C ªAIR BAGº Warning Lamp Does Not Come ªONº Steady
StepActionYe sNo
11. When measurements are requested in this chart,use
5±8840±0285±0 DVM with correct terminal adapter from
5±8840±0385±0.
2. Ignition switch ªOFF.º
3. Remove and inspect ªC±10º fuse (meter) to the ªAIR BAGº
warning lamp.
Is fuse good?
Go to Step 2Go to Step 7
21. Ignition switch ªOFF.º
2. Disconnect SRS coil and passenger air bag assemblies.
Yellow 2±pin connector located at base of steering column and
behind the glove box assembly.
3. Disconnect SDM.
4. Ignition switch ªON.º
5. Measure voltage on SDM harness connector from terminal ª7º
to terminal ª6º (ground).
Is system voltage present on terminal ª7º?
Go to Step 4Go to Step 3
31. Ignition switch ªOFF.º
2. Remove instrument meter cluster.
3. Check for proper connection to instrument cluster at
IB04±WHT/RED terminal.
4. If ok, then remove and inspect ªAIR BAGº bulb.
Is bulb good?
Go to Step 5
Replace bulb
Go to Step 6
41. Ignition switch ªOFF.º
2. Disconnect instrument meter cluster harness connector.
3. Ignition switch ªON.º
4. Measure voltage on SDM harness connector from terminal ª7º
to terminal ª6º (GROUND).
Is voltage 1 volt or less?
Go to Chart A
Replace SRS
harness
Go to Step 6
51. Install bulb.
2. Measure resistance from instrument meter cluster harness
connector IB04±WHT/RED terminal to SDM harness
connector terminal ª7º.
Is resistance 5.0 ohms or less?Service
instrument meter
cluster
Install instrument
meter cluster
Go to Step 6
Replace SRS
harness
Go to Step 6
6Reconnect all SRS components, ensure all components are
properly mounted.
Was this step finished?Repeat the ªSRS
Diagnostic
System Checkº
Go to Step 6
7Perform chart C.
Was this step finished?
Go to Step 8Go to Step 1
81. Replace ªC±10º fuse.
2. Ignition switch ªONº wait 10 Seconds then ignition switch ªOff.º
3. Remove and inspect ªC±10º fuse.
Is fuse good?
Install ªC±10º
fuse
Go to Step 10
Go to Step 9

RESTRAINT CONTROL SYSTEM 9J1±12
Chart C ªAIR BAGº Warning Lamp Does Not Come ªONº Steady (Cont'd)
StepNo Ye s Action
91. Disconnect SRS coil and passenger air bag assemblies.
Yellow 2±pin connectors located at base of steering column
and behind the glove box assembly.
2. Disconnect SDM.
3. Replace ªC±10º fuse.
4. Ignition switch ªONº wait 10 seconds.
5. Ignition switch ªOFFº.
6. Remove and inspection ªC±10º fuse.
Is fuse good?
InstallªC±10º fuse
Go to Chart A
Replace SRS
harness
Replace ªC±10º
fuse
Go to Step 10
10Reconnect all SRS components, ensure all components are
properly mounted.
Was this step finished?Repeat the ªSRS
Diagnostic
System Checkº
Go to Step 10

9J1±13
RESTRAINT CONTROL SYSTEM
DTC 15 Passenger Deployment Loop Resistance High
D09RW014
Circuit Description:
When the ignition switch is turned ªONº, the SDM will
perform tests to diagnose critical malfunctions within
itself. Upon passing these tests ªIgnition 1º, and
deployment loop voltages are measured to ensure they
are within their respective normal voltage ranges. The
SDM then proceeds with the ªResistance Measurement
Testº. ªPassenger Bag Lowº terminal ª16º is grounded
through a resister and the passenger current source
connected to ªPassenger Bag Highº terminal ª15º allows a
known amount of current to flow. By monitoring the
voltage difference between ªPassenger Bag Highº and
ªPassenger Bag Lowº the SDM calculates the combined
resistance of the passenger air bag assembly, harness
wiring IB07±YEL/GRN and IB08±YEL/RED connector
terminal contact.
DTC Will Set When:
The combined resistance of the passenger air bag
assembly, harness wiring IB07±YEL/GRN and
IB08±YEL/RED, and connector terminal contact is above
a specified value. This test is run once each ignition cycle
during the ªResistance Measurement Testº when:
1. No ªhigher priority faultsº are detected during
ªTurn±ONº,
2. ªIgnition 1º voltage is in the specified value.
Action Taken:
SDM turns ªONº the ªAIR BAGº warning lamp and sets a
diagnostic trouble code.
DTC Will Clear When:
The ignition switch is turned ªOFF.º
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 SDM.
3. This test verifies proper connection of the yellow
2±pin connector.
4. This test checks for proper contact and/or corrosion
of the yellow 2±pin connector terminals.
5. The test checks for a malfunctioning passenger air
bag assembly.
6. This test determines whether the malfunction is due
to high resistance in the wiring.
Diagnostic Aids:
An intermittent condition is likely to be caused by a poor
connection at the passenger air bag assembly harness
connector terminals ª1º and ª2º, SDM terminal ª15º and
ª16º, or a poor wire to terminal connection in
IB07±YEL/GRN and IB08±YEL/RED. This test for this
diagnostic trouble code is only run while the ªAIR BAGº