If he has running lights and the rear sensor is out of postion,,,He would still have a brake light by applying the front brake lever,
correct lever postioning and rear brake leveling pics and specs are in the manual.,,,,Unless [got busa] is talking about something different that im not aware of,,,,Since his brake light isnt stuck on ,because of misaligned rear/front switch,,,then he would have a brake light come on when applying the front brake,,,,I'd swap out the bulb first,,,,Im not at my bike to see what else runs on that fuse,,but I doubt thats the problem,,I;d swap out the bulb,,,,looks can be decieving,,,,Got busa may be right,,but I dont know of any other sensor,,