My son has replaced the multifunction switch and relay. I checked the fuses and continuity is fine. Load tested the battery and that's good too. Somewhere the wiring is giving a problem but we don't know where to start. Not showing any codes, had that checked too just in case. The headlights and taillights having been getting progressively worse. For a while they would only work when the car was warm?.? I have a couple idea but I need some more qualified opinions to diagnose. Please give me a few ideas. Thank you.