Subaru Legacy IV (2008 year). Service manual — part 1044

SB-14

Seat Belt Warning System

SEAT BELT SYSTEM

4. Seat Belt Warning System

A: WIRING DIAGRAM

<Ref. to WI-125, WIRING DIAGRAM, Seat Belt Warning System.>

B: INSPECTION

CAUTION:
• Before diagnosing the airbag system, be sure to turn the ignition switch to OFF, disconnect the
ground cable from the battery, and wait 20 seconds or more before starting to work.
• When replacing the airbag module, seat belt pretensioner, roll connector, control module and sen-
sor, reconnect each part and check that the warning light operates properly.
• When inspecting the airbag main harness, disconnect the airbag module connectors of the driver’s
and passenger’s seats for safety.
• When inspecting the airbag rear harness, disconnect the side airbag module connector, curtain
airbag module connector and seat belt pretensioner connector for safety reasons.
TROUBLE SYMPTOM:
• Driver’s side seat belt warning light does not turn on or off.
• Warning buzzer does not beep.

Step

Check

Yes

No

1

CHECK CURRENT SETTINGS.
1) Prepare the Subaru Select Monitor.
2) Turn the ignition switch to ON (engine OFF)
and run the “PC application for Subaru Select
Monitor”.
3) Select “Current Data Display” and read the
data of “Belt Warning Switch”.

Is the belt warning display ON? Go to step 2.

Turn the belt warn-
ing ON with unit
customization.

2

CHECK CURRENT DATA.
1) Select “Current Data Display” and read the
data of “IG power supply voltage”.
2) Turn the ignition switch ON

mo OFF.

Does the voltage change
between 10 V or higher

mo

less than 1.5 V, matching the
ignition switch ON

mo OFF

operation?

Go to step 3.

Check the ignition
switch circuit.

3

CHECK FUNCTION.
1) Sit in the driver’s seat and passenger’s seat,
and disconnect the seat belts of both seats.
2) Turn the ignition switch to ON (engine OFF).
3) Check the illumination of the driver’s seat
belt warning light and map light in the combina-
tion meter and the passenger’s seat belt warn-
ing light in the clock unit, and the sounding of
the buzzer.

Do the driver’s and passenger’s
warning lights flash, and does
the buzzer sound while the
warning lights are flashing?

Go to step 4.

• Malfunction of
the driver’s seat
belt warning light
oGo to step 10.
• Malfunction of
the passenger’s
seat belt warning
light

oGo to step

16.
• The buzzer does
not sound.

o Go to

step 6.

4

CHECK FUNCTION.
1) Wait until the buzzer sound stops in step 3.
(Approximately 6 seconds from starting to
sound)
2) Fasten and detach the driver’s and passen-
ger’s seat belts.
3) Check the illumination of the driver’s seat
belt warning light and map light in the combina-
tion meter and the passenger’s seat belt warn-
ing light in the clock unit, and the sounding of
the buzzer.

Do each seat belt warning light
illuminate

mo turn off accord-

ing to the action?

Go to step 5.

• Malfunction of
the driver’s seat
belt warning light
oGo to step 6.
• Malfunction of
the passenger’s
seat belt warning
light

oGo to step

12.

SB-15

Seat Belt Warning System

SEAT BELT SYSTEM

5

CHECK FUNCTION.
1) Wait until the buzzer sound stops in step 3.
(Approximately 6 seconds from starting to
sound)
2) Start the engine, and set the vehicle speed
to 15 km/h (9 MPH) or faster.
3) Check the driver’s and passenger’s seat belt
warning lights, and sounding of the alarm
buzzer.

Do the driver’s and passenger’s
warning lights flash, and does
the buzzer sound while the
warning lights are flashing?

The seat belt warn-
ing system is nor-
mal.

Go to step 19.

6

CHECK CURRENT DATA.
1) Select “Current Data Display” and read the
data of the driver’s seat belt switch.
2) Connect and disconnect the seat belt
buckle.

Does the seat belt SW display
turn ON

mo OFF according to

the operation?

Go to step 10.

Go to step 7.

7

CHECK HARNESS.
1) Disconnect the negative terminal from the
battery, and wait for 20 seconds or more.
2) Disconnect the connectors of the body inte-
grated unit and the seat belt buckle switch.
3) Check for a short circuit to battery, open cir-
cuit or short circuit to ground between the body
integrated unit and the seat belt buckle switch
LH.

Connector & terminal

(B281) No. 16 — (R108) No. 3:

Is the harness normal?

Go to step 8.

Repair or replace
the harness.

8

CHECK HARNESS.
Measure the resistance between the seat belt
buckle switch LH and chassis ground.

Connector & terminal

(R108) No. 1 — Chassis ground:

Is the resistance less than 10

:? Go to step 9.

Repair or replace
the harness.

9

CHECK SEAT BELT BUCKLE SWITCH LH.
Measure the resistance between the connector
terminals of the driver’s seat belt switch when
the driver’s seat belt is fastened and detached.

Connector & terminal

(R108) No. 1 — (R108) No. 3:

Is the resistance when the belt
is fastened 1 M

: or more, and

less then 10

: when the belt is

detached?

Replace the body
integrated unit.
<Ref. to SL-56,
REMOVAL, Body
Integrated Unit.>

Replace the inner
belt assembly LH.
<Ref. to SB-18,
INNER SEAT BELT
ASSEMBLY,
REMOVAL, Front
Seat Belt.>

10

CHECK DTC.
Read the DTC using the Subaru Select Monitor.

Are any body CAN related DTC
detected?

Check the CAN
according to DTC.

Go to step 11.

11

CHECK COMBINATION METER.
Perform the self-diagnosis of combination
meter. <Ref. to IDI-5, SELF-DIAGNOSIS,
INSPECTION, Combination Meter System.>

At the start of combination
meter self diagnosis, did the
buzzer sound and the seat belt
warning light illuminate?

Replace the body
integrated unit or
the combination
meter. Or, replace
both. There may
be a communica-
tion malfunction of
the body integrated
unit, or a reception
malfunction of the
combination meter.

Replace the com-
bination meter.
<Ref. to IDI-22,
REMOVAL, Com-
bination Meter.>

12

CHECK CURRENT DATA.
1) Sit on the passenger’s seat.
2) Select “Current Data Display” and display
the data of “P seatbelt SW input ”.
3) Fasten and detach the passenger’s side
seat belt buckle, and read the data of the seat
belt switch. <Ref. to LAN(diag)-29, OPERA-
TION, Read Current Data.>

Does the seat belt switch dis-
play turn ON

mo OFF accord-

ing to the operation of the seat
belt buckle?

Go to step 16.

Go to step 13.

Step

Check

Yes

No

SB-16

Seat Belt Warning System

SEAT BELT SYSTEM

13

CHECK AIRBAG SYSTEM AND OCCUPANT
DETECTION SYSTEM.
Perform the check in accordance with the diag-
nostic procedure DTC 27 of the airbag system.
<Ref. to AB(diag)-60, DTC 27 ODS COMMUNI-
CATION ERROR, Diagnostic Chart with Trouble
Code.>

Is there any problem on the
inspection result?

Go to step 14.

Repair or replace
the harness.

14

CHECK BUCKLE SWITCH RH.
Perform the check in accordance with the diag-
nostic procedure DTC 37 of the occupant
detection system. <Ref. to OD(diag)-27, DTC
37 BUCKLE SWITCH RH FAILURE, Diagnostic
Procedure with Diagnostic Trouble Code
(DTC).>

Is there any problem on the
inspection result?

Go to step 15.

Repair or replace
the harness.

15

CHECK AIRBAG CONTROL MODULE AND
BODY INTEGRATED UNIT.
Check the airbag control module, occupant
detection sensor and seat belt buckle switch
RH.
Perform the check in accordance with the diag-
nostic procedure DTC 39 of the airbag system.
<Ref. to AB(diag)-62, DTC 39 SEAT BELT
WARNING FAILURE, Diagnostic Chart with
Trouble Code.>

Is there any problem on the
inspection result?

Replace the body
integrated unit.
<Ref. to SL-56,
REMOVAL, Body
Integrated Unit.>

Repair or replace
the harness.

16

CHECK HARNESS.
1) Disconnect the connector of map light.
2) Turn the ignition switch to ON.
3) Measure the voltage between the body inte-
grated unit and map light.

Connector & terminal

(R150) No. 8 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step 17.

Repair or replace
the harness.

17

CHECK HARNESS.
1) Turn the ignition switch to ON.
2) Disconnect the connector of body inte-
grated unit.
3) Check for short circuit to battery, open cir-
cuit and short circuit to ground between the
body integrated unit and the map light.

Connector & terminal

(B280) No. 27 — (R150) No. 5:

Is the harness normal?

Go to step 19.

Repair or replace
the harness.

18

CHECK MAP LIGHT.
1) Connect the map light.
2) Turn the ignition switch to ON.
3) Use an appropriate wiring harness to create
a short between the body integrated unit and
the map light.

Connector & terminal

(R150) No. 5 — Chassis ground:

Does passenger’s seat belt
warning light in the map light
illuminate?

Replace the body
integrated unit.
<Ref. to SL-56,
REMOVAL, Body
Integrated Unit.>

Replace the map
light. <Ref. to IDI-
28, REMOVAL,
Clock.>

19

CHECK DTC.
Read the DTCs for all systems using the Sub-
aru Select Monitor.

Is a DTC detected?

Perform a check
according to the
DTC.

Go to step 20.

Step

Check

Yes

No

SB-17

Seat Belt Warning System

SEAT BELT SYSTEM

20

CHECK CURRENT DATA.
Select “Current Data Display” and read the data
of the “Front Wheel Speed”. <Ref. to LAN(diag)-
29, OPERATION, Read Current Data.>

Does the data indicate the nor-
mal vehicle speed?

Go to step 11.

Check the follow-
ing items.
• LAN system
<Ref. to
LAN(diag)-65,
DTC U1223 CAN-
HS VDC/ABS NO-
RECEIVE DATA,
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
• Check VDC or
ABS.

• VDC <Ref. to
VDC(diag)-2,
Basic Diagnos-
tic Procedure.>
• ABS <Ref. to
ABS(diag)-2,
Basic Diagnos-
tic Procedure.>

Step

Check

Yes

No