Page 1246 of 1449

SRS -General InformationSRS -General Information52B-2
GENERAL INFORMATION
To improve safety, the SRS and seat belts with
pre-tensioner. These systems enhance collision
safety by restraining the front passengers in case
of an accident. The SRS works with the
pre-tensioner simultaneously when a collision is
detected.
The SRS consists of two air bag modules, SRS
air bag control unit (SRS-ECU), SRS warning lamp
and clock spring. The air bags are located in the
center of the steering wheel, above the glove box.
Each air bag has a folded air bag and an inflator
unit. The SRS-ECU under the floor console monitors
the system and has a safing G-sensor and an
analog G-sensor. The warning lamp on theinstrument panel indicates the operational status
of the SRS. The clock spring is installed in the
steering column. The seat belt pre-tensioner is built
into the front seat belt retractor. Only authorized
service personnel should do work on or around
the SRS components and seat belt with
pre-tensioner. Those service personnel should read
this manual carefully before starting any such work.
Extreme care must be used when servicing the
SRS to avoid injury to the service personnel (by
inadvertent deployment of the air bags or
inadvertent operation of the seat belt with
pre-tensioner) or the driver (by rendering the SRS
or the seat belt with pre-tensioner inoperative).
Diagnosis
connectorFront passenger’s
air bag module
Clock spring Driver’s air bag
module
SRS-ECU
SRS warning lamp
Driver’s air bag
Front
passenger’s
air bag
Seat belt with
pre-tensioner
Page 1247 of 1449

SRS -SRS Service Precautions52B-3
SRS SERVICE PRECAUTIONS
1. In order to avoid injury to yourself or others
from accidental deployment of the air bag and
accidental operation of the seat belt with
pre-tensioner during servicing, read and
carefully follow all the precautions and
procedures described in this manual.
2. Do not use any electrical test equipment on
or near SRS components, except those
specified on P.52B-6.
3. Never Attempt to Repair the Following
Components:
DSRS air bag control unit (SRS-ECU)
DClock spring
DDriver’s and front passenger’s air bag
modules
DSeat belt with pre-tensionerNOTE
If any of these components are diagnosed as
faulty, they should only be replaced, in
accordance with the INDIVIDUAL COM-
PONENTS SERVICE procedures in this
manual. (Refer to P.52B-49.)
4. After disconnecting the negative (–) battery cable,
wait 60 seconds at least before any service and
insulate the disconnected cable with tape. The SRS
retain enough voltage to deploy the air bags for a
short time even after the disconnection of the battery.
So, serious injury may result by accidental air bag
deployment if a work is done on the SRS just after
the disconnection of the battery.
5. Do not attempt to repair the wiring harness connectors
of the SRS. If the connector(s) are diagnosed as defective,
replace the wiring harness(es). If the harness(es) are
diagnosed as faulty, replace or repair the wiring
harness(es) according to the table that follows.
Insulating tape
Battery
SRS-ECU connector
Page 1248 of 1449

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.
Page 1250 of 1449

SRS -Special Tools/Test Equipment/Troubleshooting52B-6
Tool UseName Number
MB686560SRS air bag
adapter harnessDeploying front passenger’s air bag module
inside or outside vehicle
MR203491or
MB628919SRS air bag
adapter harnessDeploying driver’s air bag module inside
vehicle
TEST EQUIPMENT
ToolNameUse
Digital multi-meterChecking SRS electrical circuitry
Use multi-meter for which the maximum test
current is 2 mA or less at minimum range of
resistance measurement
TROUBLESHOOTING
STANDARD FLOW OF DIAGNOSTIC TROUBLESHOOTING
Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points.
DIAGNOSIS FUNCTION
DIAGNOSIS CODES CHECK
Connect the MUT-IIto the diagnosis connector (16-pin) under the instrument under cover, then check
diagnosis codes.
(Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points.)
ERASING DIAGNOSIS CODE
Connect the MUT-IIto the diagnosis connector and erase the diagnosis code.
Caution
Turn off the ignition switch before connecting or disconnecting the MUT-II.
SRS WARNING LAMP CHECK
1. Check that the SRS warning lamp comes on when the
ignition switch is turned ON.
2. Check that the SRS warning lamp illuminates for about
7 seconds and then goes out.
3. If this is not the cause, check the diagnosis codes.
SRS warning lamp
Page 1289 of 1449

SRS - Post-collision Diagnosis52B-45
POST-COLLISION DIAGNOSIS
Whether or not the air bags have deployed, check and service
the vehicle after collision as follows:
SRS-ECU MEMORY CHECK
1. Connect the MUT-IIto the diagnosis connector. (Refer
to GROUP 00 – How to Use Troubleshooting/Inspection
Service Points.)
Caution
Refer to that the ignition switch is LOCK(OFF) when
connecting or disconnecting MUT-II.
2. Read (and write down) all displayed diagnosis codes.
(Refer to P.52B-9.)
NOTE
If battery power supply has been shut down by the
collision, the MUT-IIcannot communicate with the
SRS-ECU. Check and, repair if necessary, the instrument
panel wiring harness before the next job.
3. Use the the MUT-IIto read the data list (how long trouble(s)
have continued and how often memory have been
erased).
Data list
NoService Data ItemApplicability
92Number indication how often the memory is cleared.Maximum time to be stored: 250
93How long problem have lasted (How long it takes
from the occurrence of the problem till the first air bag
squib igniting signal)Maximum time to be stored: 9999 minutes
(approximately 7 days)
94How long problem(s) have lasted (How long it takes
from the first air bag squib igniting signal till now.)
4. Erase the diagnosis codes and after waiting 5 seconds
or more read (and write down) all displayed diagnosis
codes. (Refer to P.52B-9.)
Page 1290 of 1449

SRS - Post-collision Diagnosis52B-46
REPAIR PROCEDURE
DEPLOYED DRIVER’S AND FRONT PASSENGER’S AIR
BAGS OR OPERATED SEAT BELT PRE-TENSIONER.
1. Replace the following parts with new ones.
DSRS-ECU (Refer to P.52B-50.)
DDriver’s air bag module (Refer to P.52B-52.)
DFront passenger’s air bag module (Refer to P.52B-52.)
DSeat belt with pre-tensioner (Refer to P.52B-61.)
2. Check the following parts and replace if malfunction is
found:
DClock spring (Refer to P.52B-52.)
DSteering wheel, steering column and intermediate
joint
(1) Check the wiring harness (built into steering
wheel) and connectors for damage, and terminals
for deformation.
(2) Check the driver’s air bag module for proper
installation to the steering wheel.
(3) Check the steering wheel for noise, binds or
difficult operation and excessive free play.
3. Check the harness for binding, connectors for damage,
poor connections, and terminals for deformation.
(Refer to P.52B-44.)
UNDEPLOYED AIR BAGS OR UNOPERATED SEAT BELT
WITH PRE-TENSIONER IN LOW-SPEED COLLISION
Check the SRS components and seat belt with pre-tensioner.
If visible damage such as dents, cracks, or deformation are
found on the SRS components and seat belt with
pre-tensioner, replace them with new ones. Concerning parts
removed for inspection, replacement with new parts and
cautions in working, refer to INDIVIDUAL COMPONENT
SERVICE, P.52B-49.
Page 1293 of 1449

SRS - Individual Component Service/Warning/Caution Labels52B-49
INDIVIDUAL COMPONENT SERVICE
If the SRS components and seat belt with pre-tensioner are to be removed or replaced as a result of
maintenance, troubleshooting etc., follow the service procedures that follow.
Caution
1. SRS components and seat belt with pre-tensioner should not be subjected to heat, so remove
the SRS-ECU, driver’s air bag module, steering wheel -air bag module,front
passenger’s air bag module, clock spring, and seat belt with pre-tensioner before drying or
baking the vehicle after painting.
DFront impact sensor, SRS-ECU, Air bag module, clock spring: 93_C or more
DSeat belt with pre-tensioner: 90_C or more
Recheck SRS system operability after re-installing them.
2. If the SRS components and seat belt with pre-tensioner are removed for the purpose of check,
sheet metal repair, painting, etc., they should be stored in a clean, dry place until they are
reinstalled.
WARNING/CAUTION LABELS
Caution labels on the SRS are attached in the
vehicle as shown. Follow label instructions whenservicing the SRS. If the label(s) are dirty or
damaged, replace with new one(s).
Steering wheel
Driver’s air bag module
Clock springFront passenger’s
air bag moduleSRS-ECU
Sun visor
Steering joint cover
Glove boxCover
Seat belt with pre-tensioner
Page 1295 of 1449
SRS - SRS-ECU52B-51
INSTALLATION SERVICE POINTS
"AASRS-ECU INSTALLATION
Caution
Be sure to install the SRS-ECU properly. Otherwise, the
SRS air bags do not activate, which results in serious
injury or death of vehicle’s occupants.
"BAPOST-INSTALLATION CHECK
1. Turn the ignition switch to ON.
2. Does the SRS warning lamp illuminate for about 7 seconds
and then go out.
Yes: The SRS warning lamp is working properly
No: Go to Troubleshooting. (Refer to P.52B-6.)
INSPECTION
1. Check the SRS-ECU and brackets for dents, cracks or
deformation.
2. Check connector for damage, and terminals for
deformation.
Caution
If a dent, crack, deformation or rust are present,
replace the SRS-ECU with a new one.
NOTE
To check the SRS-ECU in other items than described
above, go to Troubleshooting. (Refer to P.52B-6.)
SRS warning lamp