I had a similar situation. The situation arose from disconnecting the negative battery terminal. If the vehicle has remote locks like mine does, whenever you disconnect the negative battery it puts the remote lock relay into some type of default mode. If you lock and unlock the car with the remote the relay is reset and returned to normal operation.
Between your steering wheel and your instrument panel on your steering column, you will find a small rocker switch that controls the parking lights. I can't tell you why it is there, but it does turn the parking lights off and on independent of the ignition and headlight switch.
behind the headlight
The parking light is in the headlight assy.
behind the headlight
behind the headlight
Turn signal lights that double as parking (marker lights) when not blinking.
The headlights work on a totally different relay than the parking and fog lights. The headlight relay or headlight fuse is usually blown when only the parking and fog lights work.
Remove the headlight assembly and you will have access to the parking light bulb.
I would start with replacing the head light switch
headlight switch is bad
check your headlight switch
In The Subaru Legacy(Outback) Service Manual and the Chilton or Haynes Repair Manual for the Legacy & Forester 2000 thru 2006.