Subaru Legacy 2004 Service Manual page 3539

Step
1 CHECK PASSENGER'S AIRBAG MODULE.
1) Turn the ignition switch OFF, disconnect the
battery ground terminal, 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 connector
(2P) and (3P) in the test harness P.
6) Connect the battery ground terminal and
turn the ignition switch ON.
2 CHECK AIRBAG MAIN HARNESS (PASSEN-
GER'S AIRBAG HARNESS).
1) Turn the ignition switch OFF, disconnect the
battery ground terminal, and wait more than 20
seconds.
2) Disconnect the airbag resistor from con-
nector (2P) and (3P) in the test harness P.
3) Remove the instrument panel lower cover,
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. <Ref. to AB-20, Air-
bag Control Module.>
5) Measure the voltage 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 (
E: DTC 21
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 terminal from battery, and wait more than 20 seconds before starting to work.
• Before replacing the airbag module, seat belt pretensioner, roll connector, control module and
sensor, reconnect each part and confirm that the warning light operates properly.
Step
1 CHECK IF DTC 21 IS INDICATED.
Read the DTC. <Ref. to AB(diag)-30, Read
Diagnostic Trouble Code (DTC).>
Diagnostic Chart with Trouble Code
Does the airbag warning light
operate properly?
Is the voltage less than 1 V?
#
):
#
):
#
):
#
):
Is DTC 21 indicated for airbag
warning light?
AB(diag)-49
AIRBAG SYSTEM (DIAGNOSTICS)
Check Yes
Replace the pas-
senger's airbag
module. <Ref. to
AB-15, Passen-
ger's Airbag Mod-
ule.>
Replace the airbag
control module.
<Ref. to AB-20,
Airbag Control
Module.>
Check Yes
Replace the airbag
control module.
<Ref. to AB-20,
Airbag Control
Module.>
No
Go to step 2.
Replace the airbag
main harness with
body harness.
No
Perform the clear
memory mode.
<Ref. to AB(diag)-
32, Clear Memory
Mode.>