The 4x4TruckLEDs CANBUS harness prevents flashing of the LEDs on trucks that use Pulse Width Modulation to check if a headlight bulb is burned out. Unfortunately, there's no way to tell ahead of time whether a give truck is going to need a CANBUS harness or not. In our experience, it's pretty rare that the 2015-2017 F150s actually need them, but occasionally they do.