Subaru Legacy (2005 year). Manual - part 903

AB(diag)-49

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

D: DTC 16 PASSENGER’S AIRBAG FAILURE

DTC DETECTING CONDITION:
• Airbag main harness (Passenger’s side) circuit is shorted to power supply.
• Airbag module harness (Passenger’s side) circuit is shorted to power supply.
• Passenger’s airbag module is faulty.
• Airbag control module is faulty.

CAUTION:
• Before diagnosing the airbag system, be sure to turn the ignition switch OFF, disconnect the
ground cable from battery, and wait more than 20 seconds 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 connector of the driver’s
and passenger’s seats for safety reasons.
WIRING DIAGRAM:

AB-01257

AB6

  AIRBAG MODULE  
(PASSENGER SIDE)

AB9

AB9

AB10

11

10

3

4

7

8

1

2

AIRBAG CONTROL MODULE

AB6

1 2 3

4 5 6

7 8 9 10 11 12 13 14 15 16 17

18 19 20 21 22 23 24 25 26 27 28

1 2 3 4

AB(diag)-50

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

E: DTC 21 AIRBAG ECU FAILURE

DTC DETECTING CONDITION:
Airbag control module is faulty.

CAUTION:
• Before diagnosing the airbag system, be sure to turn the ignition switch OFF, disconnect the
ground cable from battery, and wait more than 20 seconds 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.

Step

Check

Yes

No

1

CHECK PASSENGER’S AIRBAG MODULE.
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Remove the instrument panel side cover on 
the passenger’s side.
3) Disconnect the connector (AB10) from 
(AB9).
4) Connect the connector (1P) in the test har-
ness P to connector (AB9).
5) Connect the airbag resistor to connectors 
(2P) and (3P) in the test harness P.
6) Connect the battery ground cable and turn 
the ignition switch to ON. 

Does the airbag warning light 
illuminate for 6 seconds and go 
off?

Replace the pas-
senger’s airbag 
module. <Ref. to 
AB-17, Passen-
ger’s Airbag Mod-
ule.>

Go to step 2.

2

CHECK AIRBAG MAIN HARNESS (PASSEN-
GER’S AIRBAG HARNESS).
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Disconnect the airbag resistor from con-
nectors (2P) and (3P) in the test harness P.
3) Remove the instrument panel lower cover 
and disconnect the connector (AB7) from 
(AB2).
4) Disconnect the connector (AB6) from air-
bag control module, and connect the connector 
(1U) in the test harness U. 
5) Measure the resistance between connector 
(2U) in the test harness U and chassis ground.

Connector & terminal

(2U) No. 3 (+) — Chassis ground (

−

):

(2U) No. 5 (+) — Chassis ground (

−

):

(2U) No. 9 (+) — Chassis ground (

−

):

(2U) No. 13 (+) — Chassis ground (

−

):

Is the voltage less than 1 V?

Replace the airbag 
control module. 
<Ref. to AB-22, 
Airbag Control 
Module.>

Replace the airbag 
main harness with 
body harness.

Step

Check

Yes

No

1

CHECK IF DTC 21 IS INDICATED.
Read the DTC. <Ref. to AB(diag)-30, Read 
Diagnostic Trouble Code (DTC).>

Does the airbag warning light 
indicate DTC21?

Replace the airbag 
control module. 
<Ref. to AB-22, 
Airbag Control 
Module.>

Perform clear 
memory mode. 
<Ref. to AB(diag)-
33, Clear Memory 
Mode.>

AB(diag)-51

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

F: DTC 22 FRONT AIRBAG FIRING OUTPUT

WIRING DIAGRAM:

This DTC is indicated when the front airbag module and the pretensioner are deployed.
Once this DTC is displayed, the memory cannot be cleared. Therefore replace the following parts.
• Airbag control module. <Ref. to AB-22, Airbag Control Module.>
• Driver’s airbag module. <Ref. to AB-16, Driver’s Airbag Module.>
• Passenger’s airbag module. <Ref. to AB-17, Passenger’s Airbag Module.>
• Front sub sensor of both sides. <Ref. to AB-26, Front Sub Sensor.>
• Front seat belt outer with pretensioner of both sides. <Ref. to SB-14, Front Seat Belt.>

AB-01200

AB6

AB18

AB17

AB26

1

2

AB9

AB10

AB21

1

4

1

2

17

16

13

14

11

10

AB2

AB7

AB38

1

1

2

1

2

2

3

4

AB9

AB2

AB38

1 2

AB17

AB6

STEERING
ROLL
CONNECTOR

AIRBAG MODULE

(DRIVER SIDE)

AIRBAG MODULE

(PASSENGER SIDE)

PRETENSIONER LH

AIRBAG CONTROL MODULE

PRETENSIONER RH

AB37

3

2

7

8

AB17

AB18

AB18

AB26

AB21

AB37

1 2

WITH 
CURTAIN AIRBAG
OR LAP SEAT BELT
PRETENSIONER

   1

   2

   3

   4

1 2 3 4

*

1

:  6

*

2

:  5

*

3

: 11

*

4

: 12

WITHOUT 
CURTAIN AIRBAG

*

1

:  2

*

2

:  1

*

3

:  5

*

4

:  6

* *

* *

1 2 3

4 5 6

7 8 9 10 11 12 13 14 15 16 17

18 19 20 21 22 23 24 25 26 27 28

7 8 9 10 11 12

13 14 15 16 17 18 19

5 6

20

1 2

3 4

7 8 9 10 11 12

13 14 15 16 17 18 19

5 6

20

1 2

3 4

1 2 3 4 5 6

7 8 9 10 11 12

1 2 3 4 5 6

7 8 9 10 11 12

(WITHOUT CURTAIN AIRBAG)

(WITHOUT CURTAIN AIRBAG)

(WITH CURTAIN AIRBAG

OR LAP SEAT BELT

PRETENSIONER)

(WITH CURTAIN AIRBAG

OR LAP SEAT BELT

PRETENSIONER)

AB(diag)-52

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

G: DTC 23 CONNECTOR TO AIRBAG ECU

DTC DETECTING CONDITION:
(AB6), (AB17) and (AB18) are not connected properly to airbag control module.

CAUTION:
Before diagnosing the airbag system, be sure to turn the ignition switch OFF, disconnect the ground 
cable from battery, and wait more than 20 seconds before starting to work.

Step

Check

Yes

No

1

CHECK POOR CONTACTS IN CONNEC-
TORS (AB6), (AB17) AND (AB18).
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Disconnect the connectors (AB6), (AB17) 
and (AB18) from airbag control module.

Is there rust or damage on the 
harness connector and the 
control module connector?

Replace the airbag 
control module. 
<Ref. to AB-22, 
Airbag Control 
Module.> Or 
replace the body 
harness with air-
bag main harness 
or replace the 
body harness with 
airbag rear har-
ness.

Go to step 2.

2

CHECK POOR CONTACTS IN CONNEC-
TORS (AB6), (AB17) AND (AB18).
1) Ensure that the connectors are firmly 
reconnected.
2) Connect the battery ground cable and turn 
the ignition switch to ON.

Does the airbag warning light 
illuminate for 6 seconds and go 
off?

Finish the diagno-
sis.

Replace the airbag 
control module. 
<Ref. to AB-22, 
Airbag Control 
Module.>