Install steps

1. Disconnect the cable from the battery negative terminal.

2. Remove rear gate trim. Refer to vacation pics, fairly well pictured.

3. Unscrew the screws holding rear garnish to the gate. 8mm deep socket is needed. There are many of these nuts - be careful to not drop them inside the gate. I dropped one and could not get out. 

4. Remove the garnish. Note you'll have to pull out the grommet securing license plate lights harness - be careful to not damage it.

5. Remove the backup lamp. 

6. Install the fog lamp in the garnish. Note, you may need to reuse the foam gasket if your fog lamp came without. It's glued to the lamp with a tape. Separate it gently from the old lamp. Put the gasket on the new lamp - I used silicone to glue it to the lamp.

7. Install the garnish back into the gate.

8. Remove both D-pillar covers. Just pull them away.

9. Drop the headliner a little bit - just pull it down in the back - it's secured with clips to the roof.

10. Time to start wiring things. If you have the OEM resistor, the stock backup lamp plug can fit into the socket on the resistor - a notch on the plug needs to be cut. The idea is to keep the ground wire, but cut the hot wire (Brown-Yellow) in front of the plug and hook up the new wire that needs to be routed all the way to the power source (fuse box). 

11. Route the new wire along stock harness and use zip ties to secure it. I chose to go on the right hand size where the stock harness is (the rear washer fluid hose is on the left) -- wiggle the wire thru the harness grommet - removing the grommet makes things easier.

12. Route the wire above the headliner to the left side (if you go on the left side right away you can skip this step).

13. Remove the cargo area trim (left side). Refer to vacation pics. Removing it completely seems difficult - I just peeled it back so I could route the wire under it. See this thread for walk thru on installing rear power outlet (which you may do at the same time, as I did!): http://legacygt.com/forums/showthread.php?t=9097

14. Pull up the rear seat bottom cushion - no need to remove it completely, just raise it to get access.

15. Remove the screw securing the perimeter part of the rear seat backrest. Raise it a little bit to get some clearance. This step might be optional, if you're able to wiggle the wire somehow thru here in step 17.

16. Remove the lower inner trim on the rear door step. Major pita. I broke mine. You need to pull it hard - try to push the clips/hooks out of their holes by wedging a screwdriver and pushing towards outside of the car.

17. Route the cable up behind the cargo side trim, under the seat backrest and along the door step. Follow the stock harness and use zip ties where appropriate.

18. Remove the instrument lower panel (under the steering wheel column) - it consist of lower and upper covers. See vacation pics. 

19. Remove the lower inner trim on the front door step. Again pita, be careful to not break it.

20. Pull back the trim on the B-pillar - just peel it back at the bottom, no need to remove it completely.

21. Route the cable to behind the B-pillar cover and along the door step and up along the stock harness to the fuse box area.

22. Separate the relay panel from fuse box - just pull it. Flip it back, so you can access wires behind it.

23. Now, in order to utilize the factory rear fog fuse (fuse #1) we need to tap into the wire. The wire comes out of the large 20-pin white plug above the fuses on the fuse box (second from the top). The wire is Blue (pin #4, forth from the left, second row). Use a vampire tap to attach a piece of new wire - ca. 15 cm is enough - we'll locate the relay close to the plug. This is the power source wire (from battery) that will power the rear fog lamp.

24. Now we need to tap two wires to the front fogs relay - the front fog relay is the one in left-bottom corner of the relay panel (right-bottom when the panel is fliped back). Tap two 25 cm wires, one to Blue-White wire (control power) behind the relay, another to Purple-Blue wire (control ground, from the front fog switch on the stalk).

25. Connect all the new wires to the new relay (using female connectors, trim wires as necessary). Battery power (from the white plug) goes to pin 30 on the relay (assuming standard Bosch-style relay), control power goes to pin 86, control ground to pin 85 and the rear fog lamp wire to pin 87.

26. Mount the relay using one of the bolts securing the fuse box to the chassis.

27. Check everything, reconnect negative terminal to the battery and see if the rear fog lamp works!!!

28. Put back everything.... 

Enjoy your uber cool rear fog lamp!