Diagnostic Aids
WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
When equipped with RPO T87, the front park and daytime running lamps share the same control circuit from the Lighting Control Module. If serial data communication is lost between the Lighting Control Module and BCM, all Park, Tail, Low Beams and License Plate Lamps will default ON with the vehicle in service mode.