SRS -SRS Service Precautions52B-4
SRS-ECU
Terminal No.Destination of harnessCorrective action
7Instrument panel wiring harness→EarthRepair or replace each wiring
harness
8Instrument panel wiring harness→Combination meter
(SRS warning lamp)
harness
9, 10Instrument panel wiring harness→Front passenger’s air bag
module
11 , 1 2Instrument panel wiring harness→Clock spring→Driver’s air bag
module)Repair or replace the dash wiring
harness. Replace clock spring.
13Instrument panel wiring harness→Junction block (fuse No.3)Repair or replace each wiring
harness
16Instrument panel wiring harness→Junction block (fuse No.2)
harness.
20Instrument panel wiring harness→Diagnosis connector
29, 30Floor wiring harnessàDriver’s seat belt pre-tensioner
27, 28Floor wiring harnessàFront passenger’s seat belt pre-tensioner
6. Inspection of the SRS-ECU harness connector should be carried out by the following procedure.
Insert the special tool (probe, MB991222, in the harness set) into the connector from harness side
(rear side), and connect the tester to this probe. If any tool than specified is used, damage to the
harness and other components will result. Furthermore, measurement should not be carried out by
touching the probe directly against the terminals from the front of the connector. The terminals are
plated to increase their conductivity, so that if they are touched directly by the probe, the plating
may break, which will cause drops in reliability.
MB991222 SRS-ECU harness connector
SRS-ECU harness connector (rear view)
7. SRS components and seat belt with pre-tensioner should not be subjected to hart, so remove the
SRS-ECU, driver’s and front passenger’s air bag modules, clock spring, and seat belt with pre-tensioner
before drying or baking the vehicle after painting.
DSRS - ECU, air bag module, clock spring : 93Æ
or more
DSeat belt with pre-tensioner : 90Æ
or more
8. Whenever you finish servicing the SRS, check warning lamp operation to make sure that the system
functions properly. (Refer to P.52B-6.)
9. Make certain that the ignition switch is LOCK (OFF) position when the MUT-IIis connected or
disconnected.
10. If you have any questions about the SRS, please contact your local distributor.
NOTE
SERIOUS INJURY CAN RESULT FROM UNINTENDED AIR BAG DEPLOYMENT, SO USE ONLY
THE PROCEDURES AND EQUIPMENT SPECIFIED IN THIS MANUAL.
SRS -Troubleshooting52B-21
OK
Measure at the C-21 SRS-ECU connector.
DDisconnect the SRS-ECU connector C-21.
DDisconnect the front passenger’s air bag module connector
C-109.
Caution
Disconnect the connector and short-circuit the squib
circuit before releasing the short bar of the SRS-ECU
connector in the following operation.
DCable bands between terminals 9, 10 and the short bar
(width:3 mm, thickness:0.5 mm) between terminals 11 and
12 and the short bar, and release the short bar.
(See Figure A.)
Caution
As the short bar may not be releasable if inserted
insufficiently, insert more than 4 mm.
DMeasure at the harness side
DContinuity check between terminals 9 and 10
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:No continuity
YESNO
Replace the front passenger’s seat air bag module (squib).
Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Front passenger’s air bag
module connector
MUT-II self-diag code
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DDisconnect the front passenger’s air bag module connector C-109
and insert the resistor harness (MB991866) behind the harness side
connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.24 output?
Check the trouble
symptoms.
NG
Check the harness between the front passenger’s air bag
module and the SRS-ECU, and repair if necessary. NG
YESNG
Correct
Check connector:C-21, C-109
Connector C-21
Figure A
Terminal
Short bar
Front view of C-21
SRS-ECU connector
(harness side).
Cable band
and etc.Section
A-A
4 mm or more
A
A
Replace the SRS-ECU.
SRS -Troubleshooting52B-22
Code No.25 Front passenger’s air bag module (squib)
systemPossible Cause
This code is output when open circuit occurs in the SRS-ECU front passenger’s
air bag (squib) circuit.
However, SRS warning lamp goes out when a normal operation is resumed
(diagnosis code is not cleared.)DOpen in the front passenger’s air bag module
(squib) circuit
DConnector improper contact
DSRS-ECU inoperable
NG
Measure at the SRS-ECU connector C-21 and front
passenger’s air bag module connector C-109 .
DDisconnect the SRS-ECU connector C-21 and the front
passenger’s air bag module connector C-109 , and
measure at the harness side.
DContinuity check between the following terminals
Connector C-21 Connector C-109
9–2
10 – 1
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:Continuity (2Ωor less)
YESNO
Replace the front passenger’s seat air bag module (squib).
MUT-II self-diag code
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DDisconnect the front passenger’s air bag module connector C-109
and insert the resistor harness (MB991866) behind the harness side
connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.25 output?
Replace the SRS-ECU.
Check the trouble
symptoms.
NG
Check the harness between the front passenger’s air bag
module and the SRS-ECU, and repair if necessary.
OKNG
Correct
Check connector:C-21, C-109
OK
Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Front passenger’s air bag
module connector
Connector C-21Connector C-109
SRS -Troubleshooting52B-24
OK
YESNO
Replace the driver’s seat belt pre-tensioner.
MUT-II self-diag code
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DDisconnect the driver’s seat belt pre-tensioner connector D-28*
1and
D-26*2and connect to the resistor harness (MB991866) behind the
harness side connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.26 output?
Replace the SRS-ECU.
Check the trouble
symptoms.
NG
Check the harness between the driver’s seat belt
pre-tensioner and the SRS-ECU, and repair if necessary.
YESNG
Correct
Check connector:D-28*1,D-26*2,C-133*1, C-112*2, C-41 Driver’s seat belt
pre-tensioner connector
Measure at the SRS-ECU connector C-41.
DDisconnect the SRS-ECU connector C-41.
DDisconnect the driver’s seat belt pre-tensioner connector
D-28*
1and D-26*2.Caution
Disconnect the connector and short-circuit the squib
circuit before releasing the short bar of the SRS-ECU
connector in the following operation.
DCable bands between terminals 29, 30 and the short bar
(width:3 mm, thickness:0.5 mm) between terminals 11 and
12 and the short bar, and release the short bar.
(See Figure A.)
Caution
As the short bar may not be releasable if inserted
insufficiently, insert more than 4 mm.
DMeasure at the harness side
DContinuity check between terminals 29 and 30
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:No continuityResistor harness
(MB991866) Dummy resistor (MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Connector C-41NG
Figure A
Terminal
Short bar
Front view of SRS-ECU
connector C-41
(harness side)
Cable
band and etc.Section
A-A
4 mm or more
A
A
NOTE
*1: L.H. drive vehicles
*2: R.H. drive vehicles
SRS -Troubleshooting52B-25
Code No.27 Driver’s seat belt pre-tensioner (squib)
systemPossible Cause
This code is output when open circuit occurs in the SRS-ECU driver’s seat belt
pre-tensioner (squib) circuit.
However, SRS warning lamp goes out when a normal operation is resumed
(diagnosis code is not cleared.)DConnector improper contact
DOpen in the driver’s seat pre-tensioner (squib)
circuit
DSRS-ECU inoperable
MUT-II self-diag code
DConnect the dummy harness (MB991865) to the resistor harness
(MB991866).
DDisconnect the driver’s seat belt pre-tensioner connector D-28*
1and
D-26*2and insert the resistor harness (MB991866) behind the harness
side connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.27 output?
YESNO
Replace the driver’s seat belt pre-tensioner.
Replace the SRS-ECU.
Check the trouble
symptoms.
NG
Check the harness between the driver’s seat belt pre-tensioner
and the SRS-ECU, and repair if necessary. NG
OK
OKNG
Correct
Check connector:D-28*1,D-26*2, C-133*1, C-112*2, C-124 Driver’s seat belt
pre-tensioner connector
Measure at the SRS-ECU connector C-41, the driver’s seat
belt pre-tensioner connector D-28*
1and D-26*2.
DDisconnect the SRS-ECU connector C-41 , the driver’s
seat belt pre-tensioner connector D-28*1and D-26*2, and
then measure at the harness side.
DContinuity check between the following terminals
Connector C-41 D-28*
1,D-26*2
29 – 2
30 – 1
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:Continuity (2Ωor less)Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Connector C-41D-28*
1,D-26*2connector
NOTE
*1: L.H. drive vehicles
*2: R.H. drive vehicles
SRS -Troubleshooting52B-27
YESNO
Replace the front passenger’s seat belt pre-tensioner.
MUT-II self-diag code
DConnect the dummy harness (MB991865) to the resistor harness
(MB991866).
DDisconnect the front passenger’s seat belt pre-tensioner connector
D-28*
1and D-26*2and insert the resistor harness (MB991866) behind
the harness side connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.28 output?
Replace the SRS-ECU.
Check the trouble
symptoms.
NG
Check the harness between the front passenger’s seat belt
pre-tensioner and the SRS-ECU, and repair if necessary. NG
Figure A
Short bar
Front view of SRS-ECU
connector C-41
(harness side)
OKNG
Correct
Check connector:D-28*1, D-26*2, C-133*1, C-112*2, C-41
Measure at the SRS-ECU connector C-41.
DDisconnect the SRS-ECU connector C-41.
DDisconnect the front passenger’s seat belt pre-tensioner
connector D-28
*1and D-26*2
.
Caution
Disconnect the connector and short-circuit the squib
circuit before releasing the short bar of the SRS-ECU
connector in the following operation.
DCable bands between terminals 27, 28 and the short bar
(width:3 mm, thickness:0.5 mm) between terminals 11 and
12 and the short bar, and release the short bar.
(See Figure A.)
Caution
As the short bar may not be releasable if inserted
insufficiently, insert more than 4 mm.
DMeasure at the harness side
DContinuity check between terminals 27 and 28
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:No continuityTerminal
Cable
band and etc.
Section
A-A
A
A
4 mm or more Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Front passenger’s seat belt
pre-tensioner connectorConnector C-41
OK
NOTE
*1: L.H. drive vehicles
*2: R.H. drive vehicles
SRS -Troubleshooting52B-28
Code No.29 Front passenger’s seat belt pre-tensioner
(squib) systemPossible Cause
This code is output when open circuit occurs in the SRS-ECU front passenger’s
seat belt pre-tensioner (squib) circuit.
However, SRS warning lamp goes out when a normal operation is resumed
(diagnosis code is not cleared.)DOpen in the front passenger’s seat pre-tensioner
(squib) circuit
DConnector improper contact
DSRS-ECU inoperable
Measure at the SRS-ECU connector C-41 , the front
passenger’s seat belt pre-tensioner connector D-28*
1and
D-26*2.
DDisconnect the SRS-ECU connector C-41 , the front
passenger’s seat belt pre-tensioner connector D-28*
1and
D-26*2, and then measure at the harness side.
DContinuity check between the following terminals
Connector C-41 D-28*
1, Connector D-26*2
28 – 2
27 – 1
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:Continuity (2Ωor less)
YESNO
Replace the front passenger’s seat belt pre-tensioner.
MUT-II self-diag code
DConnect the dummy harness (MB991865) to the resistor harness
(MB991866).
DDisconnect the front passenger’s seat belt pre-tensioner connector
D-28*
1and D-26*2and insert the resistor harness (MB991866) behind
the harness side connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.29 output?
Replace the SRS-ECU.
Check the trouble
symptoms.
NG
Check the harness between the front passenger’s seat belt
pre-tensioner and the SRS-ECU, and repair if necessary. NG
OK
OKNG
Correct
Check connector:D-28*1, D-26*2, C-133*1, C-112*2, C-41 Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Front passenger’s seat belt
pre-tensioner connector
Connector C-41Connector D-28*
1, D-26*2
NOTE
*1: L.H. drive vehicles
*2: R.H. drive vehicles
SRS -Troubleshooting52B-38
Code No.64 Front passenger’s air bag module (squib)
system (short-circuited to power supply)Possible Cause
Code No.65 Front passenger’s air bag module (squib)
system (short-circuited to earth)
This code is output when the input terminal of the SRS-ECU front passenger’s
air bag module (squib) is short-circuited to power supply (code No.64) or
short-circuited to earth (code No.65).DHarness or connector fault
DThe harness of the front passenger’s air bag
module (squib) is short-circuited to power supply
(code No.64) or short-circuited to earth (code
No.65).
DSRS-ECU inoperable
Measure at the SRS-ECU connector C-21.
DDisconnect the SRS-ECU connector C-21.
DDisconnect the front passenger’s air bag
module connector C-109 .
DMeasure at the harness side
DContinuity between terminal 9 or 10 and body
earth
Caution
Do not directly insert a probe or other
devices at the front of the connector to
avoid a possible decrease in the contact
pressure.
OK:No continuity
NO
Replace the front passenger’s seat air bag module (squib).
MUT-II self-diag code
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DDisconnect the front passenger’s air bag module connector C-109
and insert the resistor harness (MB991866) behind the harness side
connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.64 or No.65 output?
YES (when No.65 is output)YES (when No.64 is output)
Replace the SRS-ECU.
Measure at the SRS-ECU connector C-21.
DDisconnect the SRS-ECU connector C-21.
DDisconnect the front passenger’s air bag
module connector C-109 .
DIgnition switch:ON
DMeasure at the harness side
DVoltage between terminal 9 or 10 and body
earth
Caution
Do not directly insert a probe or other
devices at the front of the connector to
avoid a possible decrease in the contact
pressure.
OK:0V
NG
Replace the SRS-ECU.
Correct
Check connector:C-21, C-109
Check the trouble symptoms.
Check the harness between the front
passenger’s air bag module and the
SRS-ECU, and repair if necessary.OK
NG
OK
NG
OK
NG
Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Front passenger’s air bag
module connector
Connector C-21Connector C-21