is your an import? if so you might have to run a switch from inside car from power source i.e back of cigar lighter, with wires leading through to the boot where theres a rubber grommit you can feed it through to rear bumper, if your lucky there might be fog wiring in the rear lights to start with, it sounds worse and harder than it actually is, i had to run a seperate fog on mine as it had a major earthing problem and my brake light wires are wired to my rear fogs now and i lead a wire from the light harness (fog) to a fog light attached to my bumper, sorry for long winded explanation lol hope it helps