check engine ISUZU TROOPER 1995 Workshop Manual

9J-32 Supplemental Restraint System (SRS)
SRS DIAGNOSTIC SYSTEM CHECK
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.
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 "SRS DIAGNOSTIC SYSTEM
CHECK."
The "SRS Diagnostic System Check" must be the
starting point of any
SRS diagnostics. The "SRS
Diagnostic System Check" checks for proper "AIR
BAG"
warning lamp operation, the ability of the
DERM to communicate through the
"Serial Data" line
and whether SRS diagnostic trouble codes exist.
B. REFER TO THE PROPER DIAGNOSTIC CHART
AS
DIRECTED BY THE SRS DIAGNOSTIC
SYSTEM CHECK."
The "SRS Diagnostic System Check" 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 "SRS DIAGNOSTIC SYSTEM
CHECK" AFTER ANY REPAIR OR DIAGNOSTIC
PROCEDURES HAVE
BEEN PERFORMED.
Performing
the "SRS Diagnostic System Check"
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 "ON,""Ignition 1"
voltage is applied from the "C-22·C-23" fuse to the
DERM at the
"Ignition 1" input terminals "A9" and "A10"
and from the "C-21" fuse to the DERM at the "Redundant
Indicator Ignition 1" input terminal "B2". The DERM
responds by flashing the
"AIR BAG" warning lamp seven
times while performing tests on the
SRS.When the
engine is being cranked,
"Starter'' voltage is applied from
the
"C-1" fuse to the DERM at the "Crank" input terminal
"B10".The DERM responds by grounding the "SRS
Indicator"
output terminal "B 1" until "Starter" voltage is
removed from the "Crank" input. This results in the "AIR
BAG" warning lamp being "ON" steady during
cranking.After cranking, the DERM will flash the "AIR
BAG"
warning lamp six times and perform tests on the
SRS.
NOTES ON SYSTEM CHECK CHART ~
1. The "AIR BAG" warning lamp should flash seven
times after ignition is first turned
"ON."
2. The "AIR BAG" warning lamp should remain "ON"
steady during cranking.
3. When the "AIR BAG" warning lamp flashes four
times during
"Bulb Check" this indicates a
malfunction
in the redundant lamp driver circuitry.
These malfunctions are diagnosed by
DTC 62 chart.
4. After cranking, the "AIR BAG" warning lamp should
flash six times then go
"OFF."
5. Improper operation of the "AIR BAG" warning lamp
is indicated. This test differentiates a warning lamp
stays
"ON" condition from a warning lamp does not
come
"ON" condition.
6. 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.
7. 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 may result
in extended diagnostic time, incorrect diagnosis and
incorrect parts replacement.

Supplemental Restraint System 9J-33
SRS DIAGNOSTIC SYSTEM CHECK
STEP
ACTION YES NO
1 NOTE "AIR BAG" WARNING LAMP AS IGNITION SWITCH IS GOTOSTEP2 GOTOSTEP3 TURNED "ON."
DOES WARNING
LAMP FLASH 7 TIMES?
2 NOTE "AIR BAG" WARNING LAMP AS ENGINE IS STARTED. GOTOSTEP4 GO TO CHART D. DOES WARNING LAMP COME "ON" STEADY DURING
CRANKING?
3 DOES WARNING LAMP FLASH 4 TIMES? GOTO DTC62. GO TO STEPS.
4 NOTE "AIR BAG" WARNING LAMP AFTER STARTING. GOTOSTEP6 GOTOSTEP7 DOES WARNING LAMP FLASH 6 TIMES THEN GO "OFF"?
5 DOES WARNING LAMP COME "ON" STEADY? GO TO CHART B. GO TO CHART C.
6 IGNITION SWITCH "OFF." IF
NO SRS DIAGNOSTIC TROUBLE CODES
CONNECT SCAN TOOL TO
DATA LINK CONNECTOR, ARE DISPLAYED. GOTO STEP 8. FOLLOW DIRECTIONS AS GIVEN IN THE SCAN TOOL
INSTRUCTION MANUAL.
IGNITION SWITCH "ON."
IF HISTORY DIAGNOSTIC TROUBLE CODES
REQUEST SRS DIAGNOSTIC TROUBLE CODE DISPLAY, ARE DISPLAYED. GOTO STEP 9. RECORD ALL HISTORY DIAGNOSTIC TROUBLE CODES,
SPECIFYING AS SUCH, ON REPAIR ORDER.
7 IGNITION SWITCH "OFF." IF DIAGNOSTIC TROUBLE CODES ARE
CONNECT SCAN TOOL TO DATA LINK CONNECTOR, DISPLAYED. GOTO STEP 10. FOLLOW DIRECTIONS AS GIVEN IN THE SCAN TOOL
INSTRUCTION MANUAL. IGNITION SWITCH "ON."
REQUEST SRS DIAGNOSTIC
TROUBLE CODE DISPLAY, RECORD ALL DIAGNOSTIC TROUBLE CODES SPECIFYING
AS CURRENT OR HISTORY ON REPAIR ORDER.
8
SRS IS FUNCTIONAL AND FREE OF MALFUNCTIONS.
NO FURTHER DIAGNOSIS IS REQUIRED.
9 IGNITION SWITCH "OFP'. WHEN DTC 83 IS SET, GO TO DTC 83 CHART. WHEN DTC 84 IS SET, GO TO DTC 84 CHART. FOR ALL OTHER HISTORY DIAGNOSTIC TROUBLE CODES, REFER TO "DIAGNOSTIC AIDS" FOR THAT
SPECIFIC DIAGNOSTIC TROUBLE CODE. A HISTORY DTC INDICATES THE MALFUNCTION HAS BEEN REPAIRED OR IS INTERMITTENT.
10 DIAGNOSTIC
TROUBLE CODES ARE DISPLAYED.
IGNITION SWITCH "OFF."
WHEN DTC 51 IS SET, GO TO DTC 51 CHART. DIAGNOSE REMAINING CURRENT DIAGNOSTIC TROUBLE CODES FROM LOWEST TO HIGHEST. WHEN ONLY HISTORY DIAGNOSTIC TROUBLE CODES EXIST, REFER TO "DIAGNOSTIC AIDS" FOR THAT SPECIFIC DIAGNOSTIC TROUBLE CODE. A HISTORY DTC INDICATES THE MALFUNCTION
HAS BEEN
REPAIRED OR IS INTERMITTENT.

9J-36 Supplemental Restraint System
TABLE B
"AIR BAG" WARNING LAMP COMES "ON" STEADY
CIRCUIT DESCRIPTION
When the ignition switch is first turned "ON," "Ignition 1"
voltage is applied from the "C-21" fuse to "Redundant
Indicator Ignition 1 ,"terminal "B2", and to the "AIR BAG"
warning lamp which is connected to "SRS Indicator,"
terminal "B1". The "C-22·C-23" fuses apply system
voltage to the
"Ignition 1" inputs, terminals "A9" and
"A10". The DERM responds by flashing the "AIR BAG"
warning lamp 7 times. If "Starter" is outside of the normal
operating voltage range, the
"AIR BAG" warning lamp
will
come "ON" solid with no DTCs set. When the engine
is being cranked,
"Ignition 1" voltage is applied from the
"C-1" fuse to the DERM at the "Crank" input. The DERM
responds by grounding the
"SRS" Indicator" output until
"Starter" voltage is removed from the "Crank'' input. This
results in the
"AIR BAG" warning lamp being "ON" during
cranking.After cranking, the DERM
will flash the "AIR
BAG" warning lamp 6 times.
CHART TEST DESCRIPTION
Number(s) below refer to step number(s) on the
diagnostic table.
1. An open "C-22-C-23" fuses would cause the "AIR
BAG" warning lamp to come "ON" steady.
2. A disconnected DERM harness connector will cause
the warning
lamp to come "ON" steady via the
shorting clip from terminal "A1" to terminal "81".
3. This test checks whether the short to ground caused
the
"C-1" fuse to open.
4. This test checks for an open in the ground circuitry
to the DERM.
5. This test determines whether the short to ground is
due to a malfunctioning dual pole arming sensor or
a short
in the wiring.
6. This test checks for an open in the "Ignition 1"
circuitry to the DERM.
7. This test checks for a short from the "SRS Indicator''
circuit to ground.
8. This test checks for a short from the "Crank" input
circuit to 8+.
SRS-1 JOINT CONNECTION TO IGNITION FUSE SRS C·23 10A 1!015 '12 10 IGNITION I IGNITION 1 SWITCH
FUSE~ SRS C-24 10A .... R D
PASS.3eVLR PASS. SOURCE SENSE
PASS SlOE HIGH
PASS SlOE LOW
SERIAL DATA
SRS INDICATOR
..

9J-38-~tal Restraint System
TABLE C
"AIR BAG" WARNING LAMP DOES NOT COME "ON"
CIRCUIT DESCRIPTION
When the ignition switch is first turned "ON," "Ignition 1"
voltage is applied from the "C-21" fuse to "Redundant
Indicator Ignition 1 ,"terminal "B2", and to the "AIR BAG"
warning lamp which is connected to "SRS Indicator,"
terminal "B1".
The "C-22·C-23" fuses apply system
voltage to the "Ignition 1" inputs, terminals "A9"
and"A10". The DERM responds by flashing the "AIR
BAG"
warning lamp seven times.When the engine is
being cranked,
"Starter'' voltage is applied from the "C-1"
fuse to the DERM at the "Crank" input. The DERM
responds by grounding the
"SRS Indicator'' output until
"Starter" voltage
is removed from the "Crank" input. This
results in the "ARE BAG" warning lamp being "ON"
during cranking.After cranking, the DERM will flash the
"AIR BAG" warning lamp six times.
TO IGNITION
SWITCH
FUSEj
SRS C-24 10A-
1Bot RD
FUSE SRS C-23 10A ,. ..
CHART TEST DESCRIPTION
Number(s) below refer to step number(s) on the
diagnostic table.
1. This test confirms the integrity of the "Redundant
Indicator Ignition 1" circuit.
2. This test checks for an open in the "SRS Indicator"
circuit, instrument panel cluster circuitry, and "AIR
BAG"
warning lamp bulb.
3. This test checks whether the open is due to a bad
bulb.
4. This test determines whether the malfunction is a
short from the
"SRS Indicator'' circuit to B+.
5. This test determines whether the malfunction is an
open in the "SRS Indicator'' circuit or an open in the
instrument
panel cluster.
SRS-1 JOINT CONNECTION
1834
IGNITION 1 IGNITION 1 DRIVER SOURCE SENSE DRIVER 36VLR PASS. 36VLR
REDUNDAT
INDICATOR GROUND
PASS
SIDE HIGH
PASS
SIDE LOW
1---''""""'-------'l-----l--'1-~--'TO ~&'Jc~ELT 1833 BLU FUSE N-7-ST.,AR_TE.,_R+-'l---'1----"''"'"'-"---WHT/RED C-1 0A Al'6L ____.Jill_ BAN FUSE CONNECTOR 1819
1820
SERIAL DATA
DRIVER SIDE HIGH DRIVER SIDE LOW REDUNDANT INDICATOR
IGNITION 1
SRS INDICA TOR
•

9J-40 Supplemental Restraint System
TABLED
"AIR BAG" WARNING LAMP DOES NOT COME "ON"
STEADY DURING
CRANK
CIRCUIT DESCRIPTION
When the ignition switch is first turned "ON," "Ignition 1"
voltage is applied from the "C-21" fuse to "Redundant
Indicator Ignition
1 ,"terminal "B2", and to the "AIR BAG"
warning lamp which is connected to "SRS Indicator,"
terminal "B1". The "C-22-C-23" fuses applies system
voltage to the "Ignition 1" inputs, terminals "A9"
and"A10". The DERM responds by flashing the "AIR
BAG"
warning lamp seven times.When the engine is
being cranked,
"Starter'' voltage is applied from the "C-1"
fuse to the DERM at the "Crank" input. The DERM
responds by grounding the
"SRS Indicator'' output until
"Starter'' voltage is removed from the "Crank" input. This
results
in the "AIR BAG" warning lamp being "ON" during
cranking.After cranking, the DERM
will flash the "AIR
BAG"
warning lamp six times.
FUSE
CHART TEST DESCRIPTION
Number(s) below refer to step number(s) on the
diagnostic table.
1. This test checks for a proper signal to the "Crank"
input during cranking.
2. This test determines whether the lack of a proper
crank signal
is due to an open "Crank" input circuit or
an open power feed to the "C-1" fuse.
3. This test checks for an open in the Body Harness.
4. This test checks for an open in the SRS harness.
SRS-1
TO IGNITION SWITCH
JOINT CONNECTION ___ sR_S~C-·23~1-~---PNK.----~"~~------------~~~--~~~~---IGNITION1
IGNITION 1
FUSE~ SRS C-24 lOA loot R D
IGJ;~ION __ __.,;FU.:;.SE0------'!"------"'""""---------:1-----------S-W_IT_CH ___ SR_S_C-_22_1_DA ____ -7-----"'a"-'"-----YEL
IYOS BLK/RE
l"soDv
DRIVER 36VLR PASS. 36VLA PASS. SOURCE SENSE
REDUNDAT INDICATOR GROUND
PASS SIDE HIGH
PASS SIDE LOW
SERIAL DATA
DRIVER SIDE HIGH DRIVER SIDE LOW REDUNDANT INDICATOR IGNITION 1
SRS INDICATOR
•

Supplemental Restraint System 9J-41
TABLED
"AIR BAG" WARNING LAMP DOES NOT COME "ON"
STEADY DURING
CRANK
STEP
ACTION YES NO
1
WHEN MEASUREMENTS ARE REQUESTED IN THIS CHART IGNITION SWITCH GOTO STEP2.
USE
J-39200 DVM WITH CORRECT TERMINAL ADAPTER "OFF."
FROM J-35616-A. CHECK FOR
INSTALL C-1 FUSE.
PROPER
DISCONNECT DRIVER
AND PASSENGER INFLATOR CONNECTION AT
MODULES, YELLOW 2-WAY OR 4-WAY CONNECTORS DERM HARNESS
LOCATED NEAR THE BASE OF THE STEERING COLUMN CONNECTOR AND BEHIND THE liP COMPARTMENT DOOR ASSEMBLY. TERMINAL "B10".
DISCONNECT DERM. IF OK, THEN GO TO MEASURE VOLTAGE ON DERM HARNESS CONNECTOR CHARTA. FROM TERMINAL "B1 0" TO TERMINAL "A 1"(GROUND) WHILE
STARTING ENGINE.
IS VOLTAGE
GREATER THAN 7.25 VOLTS?
2 IGNITION SWITCH "OFF." GOTOSTEP5. GOTOSTEP3.
REMOVE G-1 FUSE.
MEASURE RESISTANCE FROM
EACH TERMINAL OF THE G-1 FUSE FUSE HOLDER TO DERM HARNESS CONNECTOR
TERMINAL "B10".
IS EITHER
MEASUREMENT 5.00 OR LESS?
3 DISCONNECT BODY HARNESS CONNECTOR. GOTOSTEP4. GOTOSTEP6.
CHECK FOR PROPER CONNECTION AT BODY HARNESS
CONNECTOR TERMINAL "4".
IF OK,
THEN MEASURE
RESISTANCE FROM EACH TERMINAL OF THE C-1 FUSE FUSE HOLDER TO BODY
HARNESS CONNECTOR TERMINAL "4"
IS EITHER
MEASUREMENT 5.00 OR LESS?
4 MEASURE
RESISTANCE FROM BODY HARNESS GOTOSTEP7. REPLACE SRS
CONNECTOR TERMINAL
"4" TO DERM HARNESS HARNESS
CONNECTOR TERMINAL "B10". GOTOSTEP7.
IS EITHER MEASUREMENT 5.00 OR LESS?
5 REPAIR OPEN IN POWER FEED TO C-1 FUSE, REFER TO GO
TO STEP?.
SECTION 8. INSTALL G-1 FUSE.
6 REPLACE BODY HARNESS. GOTOSTEP7.
7 RECONNECT ALL SRS COMPONENTS, ENSURE ALL GO TO THE "SRS DIAGNOSTIC SYSTEM
COMPONENTS
ARE PROPERLY MOUNTED. CHECK" REPEAT THE "SRS DIAGNOSTIC SYSTEM CHECK."

9J-78 Supplemental Restraint System
DTC35 ~
DISCRIMINATING SENSOR OPEN OR MISSING
CIRCUIT DESCRIPTION
During normal, non-deployment operation of SRS a
small amount of current flows through both the driver and
passenger deployment loops.The diagnostic resistors
within the dual pole arming sensor and the discriminating
sensors along with the resistance of the inflator modules
cause voltage drops within the deployment loops.The
DERM monitors the voltage at "Driver Side
Low" terminal
"B8" and "Passenger Side Low" terminal "B7' to detect
shorts or opens within the deployment loops.When the
measured voltage at either terminal is within a specified
percentage of its respective
"36 VLR" power supply
voltage for
500 milliseconds DTC 35 is set.
DTC WILL SET WHEN
The voltage measured at "Driver Side Low" terminal "B8"
and "Passenger Side Low" terminal "B7" is within a
specified percentage
of its respective "36 VLR"a power
supply voltage for
500 milliseconds. This test is run every
1
00 milliseconds during the "Continuous Monitoring"
tests.
ACTION TAKEN
DERM turns "ON" the "AIR BAG" warning lamp and sets
a diagnostic trouble code.
...
DTC WILL CLEAR WHEN
The voltages measured at "Driver Side Low" terminal
"B8" and "Passenger Side Low" terminal "B7" are both
above or
below the respective "36 VLR" power supply
voltage which sets
DTC 35.
DTC CHART TEST DESCRIPTION
Number(s) below refer to step number(s) on the
diagnostic chart.
2. This test checks for an open inside the forward LH
discriminating sensor.
3. This test checks for an open inside the
Eng-ROOM(forward LH discriminating sensor
Jumper) HARNESS.
4. This test checks for an open inside the forward RH
discriminating sensor.
5. This test checks for an open inside the Engine room
(forward
RH Discriminating Sensor Jumper)
DIAGNOSTIC AIDS
An intermittent condition is likely to be an improper
connection at any of the discriminating sensor terminals,
an open in either ground feed to the discriminating
sensors,
an open discriminating sensor interconnect
ciircuit, increased resistance
of any discriminating
sensor or decreased resistance of the dual pole arming
sensor.
SRS-1 JOINT CONNECTION ,, .
DRIVER 38VLA PASS. 38VLA PASS. SOURCE SENSE
REDUNDAT INDICATOR GROUND
PASS SIDE HIGH
f---""------o~---4--'T--:f----7-------'..,_-BLKJBLU f---.!W...----o~---4--'T--:)--ITO ~~tc~~BLU
N-:1~i7-7?--.J!2!L--wHTI!'ED Al~L __..Jlli__ BAN CONNECTOR 111t
SERIAL DATA
DRIVER SIDE HIGH DRIVER SIDE lOW REDUNDANT INDICATOR IGNffiON 1
..

Supplemental Restraint System 9J-79
,~DTC35
DISCRIMINATING SENSOR OPEN OR MISSING
STEP ACTION YES NO
1 WAS THE "SRS DIAGNOSTIC SYSTEM CHECK" PERFORMED? GOTOSTEP2. GO TO THE "SRS DIAGNOSTIC SYSTEM CHECK."
2 WHEN MEASUREMENTS ARE REQUESTED IN THIS CHART USE J-39200 DVM WITH GOTOSTEP3. GOTOSTEP7. CORRECT TERMINAL ADAPTER FROM J-35616-A. DISCONNECT DRIVER AND PASSENGER INFLATOR MODULES, YELLOW 2-WAY OR 4-WAY CONNECTORS LOCATED AT THE TOP OF THE STEERING COLUMN AND BEHIND THE 1/P COMPONENT DOOR ASSEMBLY. DISCONNECT FORWARD LH DISCRIMINATING SENSOR. CHECK FOR PROPER CONNECTION TO FORWARD LH DISCRIMINATING SENSOR AT TERMINALS "1" AND "2". IF OK THEN MEASURE RESISTANCE ON FORWARD DISCRIMINATING SENSOR FROM TERMINAL "1" TO TERMINAL "2". IS RESISTANCE LESS THAN 8.54K.Cl?
3 RECONNECT FORWARD LH DISCRIMINATING SENSOR. GOTOSTEP4. GOTOSTEP8. DISCONNECT ENG·ROOM(FORWARD LH DISCRIMINATING SENSOR JUMPER) CHECK FOR PROPER CONNECTION TO ENGINE ROOM (FORWARD LH DISCRIMINATING SENSOR JUMPER) HARNESS CONNECTOR AT TERMINAL "1" AND "2". IF OK THEN. MEASURE RESISTANCE OH ENG·ROOM FORWARD LH DISCRIMINATING SENSOR JUMPER) HARNESS CONNECTOR FROM TERMINAL "1" TO TERMINAL "2". IS RESISTANCE LESS THAN 8.540?
4
RECONNECT ENGINE ROOM (FORWARD LH DISCRININATING SENSOR JUMPER) GOTOSTEP5. GO TO STEPS. HARNESS CONNECTOR. DISCONNECT FORWARD RH DISCRIMINATING SENSOR. CHECK FOR POWER CONNECTION TO FORWARD RH DISCRIMINATING SENSOR AT TERMINALS "1" AND TERMINAL "2". IF OK THEN MEASURE RESISTANCE ON FORWARD RH DISCRIMINATING SENSOR FROM TERMNAL "1" TO TERMINAL "2". IS RESISTANCE LESS THAN 8.540?
5 RECONNECT FORWARD RH DISCRIMINATING SENSOR. DISCONNECT ENGINE ROOM GOTOSTEP6. GO TO STEP10. (FORWARD RH DISCRIMINATING SENSOR JUMPER) CHECK FOR PROPER CONNECTION TO ENGINE ROOM (FORWARD RH DISCRIMINATING SENSOR JUMPER) HARNESS CONNECTOR AT TERMINALS "1" AND "2".1F OK THEN. MEASURE RESISTANCE ON ENG·ROOM(FORWARD RH DISCRIMINATING SENSOR JUMPER) HARNESS CONNECTOR FROM TERMINAL "1" TO TERMINAL "2". IS RESISTANCE LESS THAN 8.540?
6 REPLACE SRS HARNESS. GOTOSTEP11.
7 REPLACE FORWARD LH DISCRIMINATING SENSOR. GOTOSTEP11.
8 REPLACE ENG.ROOM(FORWARD LH DISCRIMINATING SENSOR JUMPER) HARNESS. GOTOSTEP11.
9 REPLACE FORWARD RH DISCRIMINATING SENSOR. GOTOSTEP11.
10 REPLACE ENG·ROOM(FORWARD RH DISCRIMINATING SENSOR JUMPER) HARNESS. GOTOSTEP11.
11 RECONNECT ALL SRS COMPONENTS ENSURE ALL COMPONENTS ARE PROPERLY GO TO THE "SRS DIAGNOSTIC SYSTEM CHECK" MOUNTED. CLEAR SRS DIAGNOSTIC TROUBLE CODES. REPEAT THE "SRS DIAGNOSTIC SYSTEM CHECK."