You can install the lights before you do any bumper removal or install. Go out to your vehicle, unplug current ones and plug harness into new ones, attached to bumper or not. That should give you a pretty good indicator whether they work or not I imagine.I have a 2018 JL sport. got a bumper from a 2020 Gladiator. Bumper has LED fogs, when I install will they be plug and play? My JL does not have LED fogs