Subaru Legacy (2005 year). Service manual - part 917

AB(diag)-105

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

AI: DTC 81 LAP SEAT BELT PRETENSIONER FAILURE

DIAGNOSIS:
• Lap seat belt pretensioner (RH) circuit is open, shorted or shorted to ground.
• Lap seat belt pretensioner is faulty.
• Lap seat belt pretensioner harness 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 airbag warning light operates properly.
• When inspecting the airbag rear harness, disconnect the side airbag module connector, curtain
airbag module connector, seat belt pretensioner connector and lap seat belt pretensioner connector
for safety reasons.
WIRING DIAGRAM:

AB-01198

AB18

AB30

10

1

2

9

AIRBAG CONTROL
MODULE

LAP SEAT BELT
PRETENSIONER

AB18

7 8 9 10 11 12

13 14 15 16 17 18 19

5 6

20

1 2

3 4

AB30

1 2

AB(diag)-106

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

Step

Check

Yes

No

1

CHECK LAP SEAT BELT PRETENSIONER.
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Disconnect the connector (AB30) from lap 
seat belt pretensioner (RH).
3) Connect the connector (1Q) in the test har-
ness Q to connector (AB30).
4) Connect the airbag resistor to connector 
(2Q) in the test harness Q.
5) 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 lap 
seat belt preten-
sioner (RH). <Ref. 
to SB-14, OUTER 
SEAT BELT 
ASSEMBLY, 
REMOVAL, Front 
Seat Belt.>

Go to step 2.

2

CHECK AIRBAG REAR HARNESS (SIDE 
AIRBAG MODULE HARNESS RH).
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Disconnect the airbag resistor from test 
harness.
3) Disconnect the connector (AB24) from side 
airbag module (RH).
4) Disconnect the connector (AB26) from seat 
belt pretensioner.
5) Disconnect the connector (AB18) from air-
bag control module.
6) Connect the connector (1U) in the test har-
ness U to connector (AB18).
7) Measure the resistance between connector 
(5U) in the test harness U and connector (2Q) 
in the test harness Q.

Connector & terminal

(5U) No. 7 — (2Q) No. 1:
(5U) No. 5 — (2Q) No. 2:

Is the resistance less than 10 
Ω?

Go to step 3.

Replace the airbag 
rear harness with 
body harness.

3

CHECK AIRBAG REAR HARNESS.
Measure the resistance between connector 
(5U) in the test harness U and chassis ground.

Connector & terminal

(3U) No. 7 — (5U) No. 5:
(5U) No. 7 — Chassis ground:
(5U) No. 5 — Chassis ground:

Is the resistance more than 1 
M

Ω?

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

Replace the airbag 
rear harness with 
body harness.

AB(diag)-107

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

AJ:DTC 85 LAP SEAT BELT PRETENSIONER FAILURE

DIAGNOSIS:
• Lap seat belt pretensioner (RH) circuit is shorted to power supply.
• Lap seat belt pretensioner is faulty.
• Lap seat belt pretensioner harness 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 airbag warning light operates properly.
• When inspecting the airbag rear harness, disconnect the side airbag module connector, curtain
airbag module connector, seat belt pretensioner connector and lap seat belt pretensioner connector
for safety reasons.
WIRING DIAGRAM:

AB-01198

AB18

AB30

10

1

2

9

AIRBAG CONTROL
MODULE

LAP SEAT BELT
PRETENSIONER

AB18

7 8 9 10 11 12

13 14 15 16 17 18 19

5 6

20

1 2

3 4

AB30

1 2

AB(diag)-108

AIRBAG SYSTEM (DIAGNOSTICS)

Diagnostic Chart with Trouble Code

Step

Check

Yes

No

1

CHECK LAP SEAT BELT PRETENSIONER.
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Disconnect the connector (AB30) from lap 
seat belt pretensioner (RH).
3) Connect the connector (1Q) in the test har-
ness Q to connector (AB30).
4) Connect the airbag resistor to connector 
(2Q) in the test harness Q.
5) 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 lap 
seat belt preten-
sioner (RH). <Ref. 
to SB-14, OUTER 
SEAT BELT 
ASSEMBLY, 
REMOVAL, Front 
Seat Belt.>

Go to step 2.

2

CHECK AIRBAG REAR HARNESS (SIDE 
AIRBAG MODULE HARNESS RH).
1) Turn the ignition switch OFF, disconnect the 
battery ground cable, and wait more than 20 
seconds.
2) Disconnect the airbag resistor from test 
harness.
3) Disconnect the connector (AB24) from side 
airbag module (RH).
4) Disconnect the connector (AB26) from seat 
belt pretensioner.
5) Disconnect the connectors (AB17) and 
(AB18) from airbag control module.
6) Connect the connector (1U) in the test har-
ness U to connector (AB18).
7) Connect the battery ground cable and turn 
the ignition switch to ON.
8) Measure the voltage between connector 
(5U) in the test harness U and chassis ground.

Connector & terminal

(5U) No. 7 (+) — Chassis ground (

−

): 

(5U) No. 5 (+) — Chassis ground (

−

): 

Is the voltage less than 1 V?

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

Replace the airbag 
rear harness with 
body harness.