Daytime Running Lamps

The daytime running lamps are combined with the park lamps. The daytime running lamps will operate when the following conditions are met:

• Engine is running.
• Headlamp switch in AUTOMATIC LIGHT position.
• The high and low beam headlamps are OFF.

Daytime Running Lamps With CE1 

The rain/ambient light sensor module is used to monitor outside lighting conditions. The rain/ambient light sensor module provides a serial data message to the BCM based on outside lighting conditions to determine if outside lighting conditions are correct for either daytime running lamps or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the designated daytime running lamps ON. During low light conditions the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel daytime running lamps operation.

Daytime Running Lamps Without CE1 

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 and 4.9 V depending on outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light sensor and the HVAC control module provides 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 headlamp switch is in the AUTO position. In daylight conditions the BCM will command the daytime running lamps ON. During low light conditions the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel daytime running lamps operation.

T4A/X88 with T4F or T4L 

In daylight conditions, the BCM will command the daytime running lamps ON by supplying B+ to the daytime running lamps control circuit, illuminating the left and right daytime running lamp LEDs. Any function or condition that turns on the headlamps will cancel daytime running lamps operation.

Z88 with T4F or T4L 

In daylight conditions, the BCM will command the daytime running lamps ON by supplying B+ to the left and right multifunction LED control modules, which illuminate the daytime running lamp LEDs.

No parts are serviceable within the headlamp assemblies so complete headlamp assembly replacement is necessary. (T4L)