Hello there. Mystery going on here. 2021 Kenworth T680. 210k miles. Paccar engine. The running lights don't work as running lights. They DO work when using turn signal and flashers. Problem started yesterday morning. 6 lights in all - 1 in each fender and 2 in each headlight assembly. Checked the bulbs, nothing burned out. Light switch in cab has 3 settings-off, running lights on, headlights and running lights on. Flipping switch to either ON position dims dash as normal. Onboard computer/s updated in December 21. No warnings or faults. Can't find which fuse or module to check. Next step will be disconnect the battery. Any ideas? Thanks.