Test the tail lights, brake lights, and turn signals. Ours worked just fine, but if the turn signals do not flash you'll need to upgrade your flasher to a heavy-duty electronic flasher from your local parts store. Ours was upgraded when we installed the aftermarket wire harness. Now, if you are replacing both front and rear or do not have front bulbs, you'll need a no-load flasher like Dakota Digital's PN LAT-NLF. Keep that in mind when ordering parts.