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.

The daytime running lamps will illuminate continuously when the following conditions are met:

Ignition ON, vehicle running
The Turn Signal Switch is in the AUTO position
Ambient light conditions are daytime brightness

Daytime Running Lamps

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 V and 4.9 V depending on outside lighting conditions. The BCM provides a 5 V reference signal to the ambient light sensor and a low reference ground. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps or automatic lamp control when the Turn Signal Switch is in the AUTO position. In daylight conditions the BCM will send a serial data message to the Lighting Control Module to command the daytime running lamps ON. During low light conditions the Lighting Control Module will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel daytime running lamps operation. 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.