The fog lights like to burn out. And also the ground clip works loose and can cause the lamp to not come on, or burnout prematurely. The was a TSB to replace the harness, but most GXP'* are no longer under warranty. I think the loose ground had more to do with them burning out anyway. Two ways to get at them.....
There are two ways to get at these elusive lamps.
1. Remove the inner fender by releasing the button clips. They come out by prying the center pin out first, then the entire clip will come out easily. Turn the front wheels to allow access to the fog lamps. Then remove the connector housing and, release the wire clip holding the bulb in place.
2. Remove the headlamp assembly (3 - 7mm bolts) Then remove the connector housing and, after alot of fumbling because you can't see, release the wire clip holding the bulb in place.
Either way, when replacing, you must thread the attached wire THROUGH THE CLIP before inserting the bulb.
Silicone the O-ring and and dry the inside of the housing with a hair dryer before re-assembly. There is obviously a design flaw here. Check the ground wire and make sure it is firmly attached.