
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-7
SRS SYSTEM CIRCUIT DIAGRAM
Ignition switch (IG1)
J/B
(common fuse)
Combination
Meter
Connector lock switch*
ON
ON OFF
OFF
Driver’s air
bag module
(squib)
Front pas-
senger’s seat
air bag mod-
ule(squib)
Seat belt
pre-tensioner
(L.H.)Clock spring
ONONOFF
OFF
Connector lock switch* Diagnosis connector SRS-ECU
No.3
7.5A No.2
7.5A
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFFON
ON
ON
ON
ON
ON
ON
ONOFF
ON
ON OFF
C-207
C-204
C-109
D-28
D-26C-22
SRS - ECU connector16
13
7 8
11
12
10
9
30
29
28
2720 Connector lock switch*
Connector lock switch*
Connector lock switch*
Connector lock switch*
Connector lock switch*
NOTE
*:connector engaged:ON
connector disengaged:OFF Seat belt
pre-tensioner
(R.H.)

SRS -Troubleshooting52B-10
Code no.Page Diagnostic item
34*2Connector lock system52B-29
35SRS-ECU (deployed air bag) system52B-29
41*2Power supply circuit system (fuse No.2 circuit)52B-30
42*2Power supply circuit system (fuse No.3 circuit)52B-32
43*2SRS warning lamp drive circuit systemLamp does not illumi-
nate.52B-33
SRS warning lamp drive circuit systemLamp does not go out.52B-33
44*2SRS warning lamp drive circuit system52B-33
45SRS-EUC internal circuit system including non - volatile memory (EEPROM)52B-11
51Driver’s air bag module (squib) ignition drive circuit systemShort in the ignition
drive circuit52B-11
52Driver’s air bag module (squib) ignition drive circuit systemOpen in the ignition
drive circuit
54Front passenger’s air bag (squib) ignition drive circuit
systemShort in the ignition
drive circuit52B-11
55Front passenger’s air bag (squib) ignition drive circuit
systemOpen in the ignition
drive circuit
56Driver’s seat belt pre-tensioner (squib) ignition drive circuit
systemShort in the ignition
drive circuit52B-11
57Driver’s seat belt pre-tensioner (squib) ignition drive circuit
systemOpen in the ignition
drive circuit
58Front passenger’s seat belt pre-tensioner (squib) ignition
drive circuit systemShort in the ignition
drive circuit52B-11
59Front passenger’s seat belt pre-tensioner (squib) ignition
drive circuit systemOpen in the ignition
drive circuit
61Driver’s air bag module (squib) systemShort-circuited to
power supply52B-34
62Driver’s air bag module (squib) systemShort-circuited to earth
64Front passenger’s air bag module (squib) systemShort-circuited to
power supply52B-38
65Front passenger’s air bag module (squib) systemShort-circuited to earth
66Driver’s seat belt pre-tensioner (squib) systemShort-circuited to
power supply52B-39
67Driver’s seat belt pre-tensioner (squib) systemShort-circuited to earth
68Front passenger’s seat belt pre-tensioner (squib) systemShort-circuited to
power supply52B-40
69Front passenger’s seat belt pre-tensioner (squib) systemShort-circuited to earth
NOTE
(1) *1: If the trouble(s) are removed, the SRS warning lamp go out with diagnosis code history stored.
(2) *2: If the trouble(s) are removed, the SRS warning lamp will go out with diagnosis code history automatically erased.
(3) When the battery has been discharged, diagnosis code No.41 or 42 is stored. Check the battery when either of
these is displayed.

SRS -Troubleshooting52B-30
Code No.41 Power supply circuit system (fuse No.2
circuit)Possible Cause
This codes output when the voltage between terminal IG1(SRS-ECU, terminal
No.16) and earth has been below the standard value for 5 seconds.
However, code No.41 is automatically erased and SRS warning lamp goes out
when a normal operation is resumed. If code No.41 and 42 are output at the
same time, check the battery first since the battery voltage may have decreased.DHarness or connector fault
DSRS-ECU inoperable
Measure at the junction block connector
C-213.
DDisconnect the junction block connector
C-213 and measure at the harness
side.
DContinuity check between terminal 25
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
Measure at the junction block connector C-213.
DDisconnect the junction block connector C-213 and
measure at the harness side.
DContinuity check between terminal 24 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
NGCorrect the harness between the junction block and
combination meter (SRS warning lamp).
NGOK
NGNG
Check the trouble symptoms.Correct
Check the harness between the SRS-ECU and the ignition
switch IG
1, and repair if necessary. Fuse is normal
NG
Fuse disconnection
Check the junction block general fuse No.2.
Fuse disconnection
Check when fuse disconnects
DReplace the fuse.
DTurn the ignition switch to the ON position and then turn it
to the OFF position after one minute or more has passed.
Check the fuse.
OK
OK
Replace the SRS-ECU.
DDisconnect the SRS-ECU connector C-21.
DConnect the negative ( - ) terminal of the battery
DIgnition switch: ON
DMeasure at the harness side
DVoltage between terminal 16 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:9 V or more
Check the other circuits using the general fuse No.2.
(See the Electrical Wiring Diagram.) OK
Check connector:C-21, C-213, C-210
Go to Next PageConnector C-21
Connector C-213
Connector C-213

SRS -Troubleshooting52B-32
Code No.42 Power supply circuit system (fuse No.3
circuit)Possible Cause
This code is output when the voltage between terminal IG1(SRS-ECU, terminal
No.13) and earth has been below the standard value for 5 seconds.
However, code No.42 is automatically erased and SRS warning lamp goes out
when a normal operation is resumed.If code No.41 and 42 are output at the
same time, check the battery first since the battery voltage may have decreased.DHarness or connector fault
DSRS-ECU inoperable
OK
Check the other circuits using the general
fuse No.3. (See the Electrical Wiring
Diagram.)
NGOK
NG
NG
NG
Check connector:C-21, C-213, C-210
Check the trouble
symptoms.Correct
Check the harness between the SRS-ECU and the ignition
switch IG
1, and repair if necessary.
NG
Fuse disconnection
Fuse disconnection
OK
Replace the SRS-ECU.
1
>Measure at the SRS-ECU connector C - 21.
DDisconnect the SRS-ECU connector C-21 and measure at
the harness side.
DConnect the negative ( - ) terminal of the battery
DIgnition switch: ON
DVoltage between terminal 13 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:9 V or more
OK
Check the harness between the SRS-ECU and junction block,
and repair if necessary.
Measure at the C-21 SRS-ECU connector.
DDisconnect the SRS-ECU connector C-21 and measure at
the harness side.
DContinuity check between terminal 13 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
Replace the SRS-ECU.Fuse is normal
Check the junction block general fuse No.3.
Check when fuse disconnects
DReplace the fuse.
DTurn the ignition switch to the ON position and then turn it
to the OFF position after one minute or more has passed.
Check the fuse.
Measure at the junction block connector C-213.
DDisconnect the junction block connector C-213 and
measure at the harness side.
DContinuity check between terminal 7 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 continuityConnector C-21
Connector C-213
Connector C-21

SWS -Special Tools/Troubleshooting54B-2
SPECIAL TOOLS
ToolNumberNameUse
MB991502MUT-II subassem-
blyFor SWS inspections (diagnosis code display
and input signal check by MUT-II)
MB991529Diagnosis code
check harnessFor checking input signals by voltmeter
A
B
C
D
MB991223
A: MB991219
B: MB991220
C: MB991221
D: MB991222Harness set
A: Test harness
B: LED harness
C: LED harness
adapter
D: ProbeFor checking voltage (continuity and value) at
harnesses and connectors
A: For checking connector pin contact voltage
B: For checking power supply circuits
C: For checking power supply circuits
D: For connection to commercially available
testers
TROUBLESHOOTING
BEFORE COMMENCING TROUBLESHOOTING
Before starting troubleshooting, check the following two points to ensure there are no defects.
DCheck the state of the connector couplings to the ETACS-ECU and junction box.
DCheck that the fuses and fusible links relating to all systems are not fused.
STANDARD FLOW OF DIAGNOSTIC TROUBLESHOOTING
Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points.
DIAGNOSTIC FUNCTIONS
READING DIAGNOSIS CODES
Read the diagnosis codes using MUT-II. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points.)
NOTE
1. Connect MUT-II to the 16-pin diagnosis connector (black).
2. The diagnosis code cannot be read when there is an ETACS-ECU fault or when the power is first
turned ON (voltage rising). In this case, refer to “No Communication with MUT-II” (P. 54B-10) on
Fault Symptom Inspection Procedure, and perform troubleshooting.