This was one of the first mods I planned after I purchased my WRX in 2012. I searched and couldn't find a DYI, so I planned to research later, got busy with other stuff, blah, blah, blah, time passed. Then I found myself 10 months later ready to move. One more search and viola! I Found it here:
DIY: 2012 WRX: Use fog lights as DRL - NASIOC
This is a very simple mod and as long as you own some ramps, it is easy to perform from under the car.
1. 1 screw/bolt and 2 plastic pop-rivets get you under car access on passenger side.
2. Use 2 Tap Splice connectors
.......one for Green DLR Wire (part of DLR resister circuit)
.......one for White/Black wire (part of Fog circuit)
3. Approximately 10" of 14 gauge wire between 2 taps.
.......Could do with 6" or so, but I used more to keep it clean and have
.......enough to cable tie to harness.
4. Leave plug to resister (step-down 12VDC-6VDC) unplugged.
.......I used tape to insulate this plug prior to cable-tieing it off to horn bracket.
5. I also changed the fogs to Luminics Krypton Series JDM Yellow bulbs
.......Performing step 1 on the driver's side gave access for the bulb change.
After buttoning things up it looked like this:
Car running, eBrake off:
.......of course ebrake on no lights at all
Car running headlights on:
Car running, headlights on, fog lights on:
.......fogs work on stalk switch, independently from the DRL function.
The yellow DRL/fogs look much more yellow in person and the night time view will rock yellow fogs when needed.
Thanks to OP, REBinc (NASIOC), for the write up!!