Circuit/System Description

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 the Turn Signal Switch is placed in the HEAD or PARK position, ground is applied to the Turn Signal Switch park lamp switch ON signal circuit to the body control module (BCM). The park lamps will also be signaled on when the Turn Signal Switch is in the auto position during night conditions. The BCM responds sending a serial data message to the Lighting Control Module. The Lighting Control Module responds by applying voltage to the park lamps, tail lamps, and license lamps control circuits illuminating the park, tail, and license lamps. If equipped with RPO T87, the daytime running lamps and front park lamps use the same serial data input from the BCM to the Lighting Control Module, additionally 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.