Headlamp: Description and Operation

HEADLAMPS ON WITH WINDSHIELD WIPERS
For vehicles equipped with the Automatic Headlamp System, the instrumentation and exterior illumination lamps will be turned ON when the headlamp switch is in the AUTO position and the windshield wipers have been in the intermittent, low or high mode of operation for more than ten seconds. When the windshield wipers are turned OFF the Body Control Module will determine if the instrumentation and exterior illumination lamps should remain ON base upon the current ambient light level.

HEADLAMP SYSTEM
The headlamp system is controlled completely by the Body Control Module (BCM). The BCM controls the Park lamps, Headlamps, and Front Fog Lamps using relays located in the Junction Block. Three wires are connected between the headlamp switch and the BCM. The first wire contains information regarding the position of the headlamp switch (Oft, Automatic Headlamps, Automatic Headlamp switch fog, Park with Fog, Head, or Head with Fog Lamps). The second wire contains information regarding the position of the dimmer switch (Dome Lamp, Daytime Brightness, or Dimming Level). The third wire is a dedicated signal return (ground) wire.

The headlamp system will default to headlamps ON position when ignition switch is ON when an open or short circuit failure occurs on the headlamp switch input. The system will return to normal operation when the open or short is repaired. A fault will be reported by the BCM when a failure occurs on the dimmer or headlamp switch input.

The dimmer system will default to Daytime Brightness when an open or a short occurs on the dimmer switch input.

The BCM will turn OFF the exterior lamps if they are left ON with the ignition switch OFF for more than ten minutes. This feature prevents the vehicle battery from being discharged when the vehicle lights have been left ON.

HEADLAMP TIME DELAY SYSTEM
The Headlamp Time Delay system is controlled by the Body Control Module (BCM) through the headlamp relay.

The headlamp time delay system is activated by turning the headlamps ON (high or low beam) while the engine is running, turning the ignition switch OFF, and then turning the headlamp switch OFF within 45 seconds. The system will not activate if more than 45 seconds elapse between ignition switch OFF and headlamp switch OFF. The BCM will allow the headlamps to remain ON for 90 seconds before they automatically turn off. Refer to the Owner's Manual for more information.