recently i had a legacy with just keyless entry and got into the habit of opening the door and locking it once i got in and then turned on the car...well forgetting that my impreza has the stock security system on it i did the same thing. i unlocked the doors/unarmed the alarm with the remote, got in the car, locked the door manually then shut the door, not realizing that armed the alarm, then i started the car and the alarm just went off and then i was able to shut it off...i looked in the manual and the security light blinks 3 times and that says it means the alarm was tampered with. is there anyway to reset the alarm? do i have to take it to a dealer? all i have now is keyless entry, no flashing lights, no horn sound....any advice???

maybe something that resetting the computer will fix? have you tried disconnecting the battery?

Did you try turning you key in the drivers door??