Subaru 2004 Legacy Owner's Manual page 123

Keys and doors
5. Close all doors (and the rear gate on the station
wagon).
1
1) Press to Arm the system.
2) Press to Disarm the system.
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2
HS2016EB
6. Briefly press the "LOCK/ARM" button (for less than
two seconds). All doors (and the rear gate on the sta-
tion wagon) will lock, an electronic chirp will sound one
time, the turn signal lights will flash one time and the
indicator light starts flashing slowly (approximately
once every two seconds).
If any of the doors, (rear gate or trunk lid) is not fully
closed, an electronic chirp sounds five times, the turn
signal lights flash five times to alert you that the doors
(or the rear gate) are not properly closed. When you
close the door, the system will automatically arm and
doors will automatically lock.
1
1) Security system indicator light
UB2033BB