Diode Dynamics Add-on DT 2-Pin Foglight Wiring HarnessOverview. Add fog lights to your vehicle. If you want to add fog lights to your vehicle but you don't have factory wiring this is the solution you need! Unlike other basic harnesses on the market our Add On Fog Harness allows your fog lights to operate automatically just like you'd expect from the factory. By using an activation and deactivation wire along with a toggle switch this harness will turn your fog lights on automatically any time the