Daimler Trucks North America LLC (DTNA) is recalling certain 2017-2020 Thomas Built Buses Saf-T-Liner C2 school buses configured with a specific Switch Hub Module (part numbers 204803 and 216434) combined with a 500k Bulk Head Module and a certain 3-position momentary switch warning light package. The Switch Hub Module (SHM) that controls the exterior warning lights and stop sign may fail, resulting in deactivation of the red warning lights, stop sign and system indicator.