2007 ISUZU KB P190 Circuit

9A1-8 RESTRAINT CONTROL SYSTEM

Circuit Description
W hen the ignition switch is first turned “ON”, “Ignition 1”
voltage is applied from the “SRS” fuse to the SRS
control unit at the “Ignition 1” input terminals “1”. The
SRS control unit responds by flashing the “SRS”
warning lamp seven times, while performing tests on
the SRS.

Notes On System Check Chart
1. The “SRS” warning lamp should flash seven times after the ignition is first turned “ON”.
2.
After the “SRS” warning lamp flashes seven times, it
should turn to “LOCK”
3. This test checks for the proper operation of the “Serial Data” line. This test will also determine
whether history diagnostic trouble codes are stored
and, if so, identify them.
4. Improper operation of the “SRS” warning lamp is indicated. This test differentiates between ‘a
warning lamp stays “ON” condition’ and ‘a warning
lamp does not come “ON” condition’.
5. This test checks for proper operation of the “Serial Data” 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
diagnostic trouble codes in the order specified ma
y
result in extended diagnostic time, incorrect diagnosis
and incorrect parts replacement.


SRS Diagnostic System Check

Step Action Yes No
1 Note the “SRS” warning lamp as the ignition switch is turned
“ON”.
Does the “SRS” warning lamp flash seven (7) times? Go to Step 2 Go to Step 3
2 Note the “SRS” warning lamp after it flashed 7 times.
Does the “SRS” warning lamp go “OFF”? Go to Step 4 Go to Step 5
3 Note the “SRS” warning lamp as the ignition switch is turned
“ON”.
Does the “SRS” warning lamp come “ON” steady? Go to Chart B. Go to Chart C.
4
1. Note the “SRS” warning lamp as the ignition switch is turned
“ON”.
Ignition switch is at “LOCK”.
2. Connect a scan tool to data link connector.
3. Follow direction given in the scan tool instruction manual.
Ignition switch is “ON”.
4. Request the SRS diagnostic trouble code display, recode all
history diagnostic trouble code(s), specifying as current or
history in repair order.
Is (are) diagnostic trouble code(s) displayed?
Ignition switch
“LOCK”.
W hen DTC B0071 is set, go to DTC B0071 Chart.
For all other history codes refer to
“Diagnostic Aids” For that specific DTC.
A history DTC indicates the
malfunction has
been repaired or is intermittent. SRS is functional
and free of
malfunctions, no
further diagnosis is required.
If scan tool
indicated “NO DATA
RECEIVED,” refer to chassis
electrical section 8.

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ISUZU KB P190 2007

9A1-10 RESTRAINT CONTROL SYSTEM

Chart A SRS Control Unit Integrity Check




RTW 79ALF000301

Circuit Description
W hen the SRS control unit recognizes that “Ignition 1”
voltage, applied to terminals “1”, is greater than 9 volts,
the “SRS” warning lamp is flashed 7 times to verif
y
operation. At this time the SRS control unit performs
“Turn–ON” tests followed by “Continuous Monitoring”
tests. W hen a malfunction is detected, the SRS control
unit sets a current diagnostic trouble code and
illuminates the “SRS” warning lamp. The SRS control
unit will clear current diagnostic trouble codes and move
them to a history file when the malfunction is no longe
r
detected and/or the ignition switch is cycled, except for
DTCs B0051 and B0055.

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 “Diagnostic Aids” for the appropriate diagnostic
trouble code should be referenced. The SRS control
unit 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 extremel
y
unlikely that a malfunctioning SRS control unit would
cause a new malfunction to occur during the
diagnostic process.

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ISUZU KB P190 2007

RESTRAINT CONTROL SYSTEM 9A1-11

3. W hen 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 has been performed. W hen 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, check the following.
2. Diagnostic procedures must be performed to verify the need
for SRS control unit replacement.
3. Ignition switch is at “LOCK”.
4. Reconnect all SRS components and ensure all components are properly mounted.
5. Ensure the ignition switch has been in the “LOCK” position for
at least 15 seconds.
6. Note the “SRS” warning lamp as the ignition switch is turned
“ON”.
Does the 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 the diagnostic trouble code display.
Is the same symptom or DTC occurring that was occurring when
the “SRS Diagnostic System Check” was first performed? Go to Step 3 Ignition switch
“LOCK”.
Go to the
appropriate chart for the indicated malfunction.
3 1. Clear the “SRS Diagnostic Trouble Codes”.
2. Ignition switch is in the “LOCK” position for at least two
minutes.
3. Note the “SRS” warning lamp as the 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
“LOCK”.
Replace SRS control unit.
Go to Step 4
4 Reconnect all SRS components, ensure all components are properly mounted.
Is this step finished? Repeat the “SRS
Diagnostic System Check” —


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ISUZU KB P190 2007

9A1-12 RESTRAINT CONTROL SYSTEM

Chart B “SRS” Warning Lamp Comes “ON” Steady




RTW 79ALF000301

Circuit Description
W hen the ignition switch is first turned “ON”, “Ignition 1”
voltage is applied from the “METER” fuse to the “SRS”,
warning lamp which is connected to “SRS W arning
Lamp”, terminal “4”. The “SRS” fuses apply system
voltage to the “Ignition 1” inputs, terminals “1”. The
SRS control unit responds by flashing the “SRS”
warning lamp 7 times. If “Ignition 1” is less than 9 volts,
the “SRS” warning lamp will come “ON” 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 “Ignition 1” circuit to the SRS control unit.
3. This test checks for the voltage of “Ignition 1”.
4. This test determines whether the malfunction is a short to ground in the SRS warning lamp circuit.



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ISUZU KB P190 2007

9A1-14 RESTRAINT CONTROL SYSTEM

Chart C “SRS” Warning Lamp Does Not Come “ON” Steady




RTW 79ALF000301

Circuit Description
W hen the ignition switch is first turned “ON”, “Ignition 1”
voltage is applied from the “METER” fuse to the “SRS”
warning lamp which is connected to the “SRS W arning
Lamp”, terminal “4”. The “SRS” fuse applies system
voltage to the “Ignition 1” inputs, terminals “35”. The
SRS control unit responds by flashing the “SRS”
warning lamp seven times. If “Ignition 1” is more than
16 volts, the “SRS” warning lamp will still be “OFF” 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 the
SRS control unit 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 SRS warning lamp circuit and
checks for a short in the SRS warning lamp circuit to
B+.
8. This test checks for a short from the SRS control
unit warning lamp power feed circuit to ground.
9. This test determines whether the short to ground is
due to a short in the wiring.


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ISUZU KB P190 2007

RESTRAINT CONTROL SYSTEM 9A1-15

Chart C “SRS” Warning Lamp Does Not Come “ON” Steady

Step Action Yes No
1
1. W hen measurements are requested in this chart, use a 5-
8840-0366-0DMM with a correct terminal adapter from 5-
8840-0385-0.
2. Ignition switch is at “LOCK”.
3. Remove and inspect the “METER” fuse to the “SRS” warning lamp.
Is the fuse good? Go to Step 2 Go to Step 7
2

1. Ignition switch is at “LOCK”.
2. Disconnect the SRS coil and passenger air bag assembly
yellow connector which is located at the base of the steering
column and behind the glove box assembly.
3. Disconnect the SRS control unit.
4. Ignition switch is “ON”.
5. Measure the voltage on the SRS control unit harness connector from the terminal “4” to terminal “3” (ground).
Is system voltage present on terminal “4”? Go to Step 4 Go to Step 3
3

1. Ignition switch is at “LOCK”.
2. Remove instrument meter cluster.
3. Check for proper connection to instrument cluster at the SRS warning lamp circuit terminal.
4. If ok, then remove and inspect the “AIR BAG” bulb.
Is the bulb good? Go to Step 5 Replace bulb.
Go to Step 6
4
1. Ignition switch is at “LOCK”.
2. Disconnect instrument meter cluster harness connector.
3. Ignition switch is “ON”.
4. Measure the voltage on the SRS control unit harness
connector from terminal “4” to terminal “3” (ground).
Is the voltage 1 volt or less? Go to Chart A Replace SRS
harness.
Go to Step 6
5
1. Install the bulb.
2. Measure the resistance from the instrument meter cluster
harness connector SRS warning lamp circuit terminal to the
SRS control unit harness connector terminal “4”.
Is the 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
6 Reconnect all SRS components and ensure all components are
properly mounted.
Is this step finished? Repeat the “SRS
Diagnostic System Check” Go to Step 6
7
Perform chart C.
Is this step finished? Go to Step 8 Go to Step 1
8

1. Replace the “METER” fuse.
2. Ignition switch is “ON”. W ait 10 Seconds then ignition switch
is at “LOCK”.
3. Remove and inspect the “METER” fuse.
Is the fuse good? Install “METER”
fuse.
Go to Step 10 Go to Step 9

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ISUZU KB P190 2007

RESTRAINT CONTROL SYSTEM 9A1-17

DTC B0015 (Flash Code 15) Passenger Air Bag Squib Circuit High Resistance




RTW 79ALF000301
Circuit Description
W hen the ignition switch is turned to “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”.
The “Passenger Bag Low” terminal “16” is grounded
through a resister and the passenger current source
connected to the “Passenger Bag High” terminal “17”
and allows a known amount of current to flow. B
y
monitoring the voltage difference between the
“Passenger Bag High” and “Passenger Bag Low” the
SRS control unit calculates the combined resistance o
f
the passenger air bag assembly, harness wiring circuits
“Passenger Bag High” and “Passenger Bag Low”
connector terminal contact.
DTC Will Set When
The combined resistance of the passenger air bag
assembly, harness wiring circuits “Passenger Bag High”
and “Passenger Bag Low”, and connector terminal
contact is above a specified value. This test is run once
for 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
The SRS control unit turns “ON” the “SRS” warning
lamp and sets a diagnostic trouble code.


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ISUZU KB P190 2007

9A1-18 RESTRAINT CONTROL SYSTEM

DTC Will Clear When
Resistance value returns specified resistance value.

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 yello
w
connector.
4. This test checks for proper contact and/or corrosion
of the yellow connector terminals.
5. This test checks for a malfunctioning passenger ai
r
bag assembly.
6. This test determines whether the malfunction is due
to a 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 “1” and “2”, SRS control unit
terminal “17” and “16”, or a poor wire to terminal
connection in circuits “Passenger Bag High” and
“Passenger Bag Low”. The test for this diagnostic
trouble code is only run while the “SRS” warning lamp is
performing the bulb check. W hen the scan tool “Clea
r
Codes” command is issued and the malfunction is still
present, the DTC will not reappear until the next ignition
cycle.


DTC B0015 (Flash Code 15) Passenger Air Bag Squib Circuit High Resistance

Step Action Yes No
1 W as the “SRS Diagnostic System Check” Performed?
Go to Step 2 Go to The “SRS
Diagnostic System Check”
2
1. Check the passenger air bag squib circuit for open.
2. If a problem is found, repair as necessary.
W as a problem found? Verify repair Go to Step 3
3

1. Ignition switch is at “LOCK”.
2. Make sure the passenger air bag assembly yellow connector
located behind the glove box assembly is seated properly.
Is the yellow connector connected properly? Go to Step 4 Seat passenger Air
Bag assembly
yellow connector properly.
Go to Step 7
4
1. Disconnect and inspect the passenger air bag assembly
yellow connector located behind the glove box assembly.
2. If OK, reconnect the passenger air bag assembly connector.
3. Ignition switch is “ON”.
Is DTC B0015 current? Go to Step 5 Go to Step 7
5

1. Ignition switch is at “LOCK”.
2. Disconnect the SRS coil and passenger air bag assembly,
yellow connector located at the base of the steering column
and behind the glove box assembly.
3. Connect a 5-8840-2421-0 SRS driver / passenger load tool
and appropriate adapters to the SRS coil and passenger air
bag assembly harness connectors.
4. Ignition switch is “ON”.
Is DTC B0015 Current? Go to Step 6 Ignition switch
“LOCK”.
Replace the
passenger air bag assembly.
Go to Step 7

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ISUZU KB P190 2007