The headlamps may be turned on two different ways. First, when the driver places the headlamp switch in the ON position, for normal operation. Second, with the headlamp switch placed in the OFF position, during Daytime Running Lamp (DRL) operation in low light conditions.

The HDLP L and HDLP R fuse in the underhood accessory wiring junction block, supply battery positive voltage to both low beam lamps and high beam lamps at all times. The low beam and high beam circuits continue to the headlamp dimmer switch , the low beam or high beam circuit is then, depending on the position of the dimmer switch, connected the headlamp switch. When the headlamp switch is placed in the ON position, it provides a ground path for the low beam or high beam lamps through G201. The headlamp switch also provides a input signal to the BCM in order to determine if the headlamps are ON.

During Daytime Running Lamp (DRL) operation in low light conditions the BCM will pull the headlamp relay low, energizing it. When the headlamp relay energizes, it provides a ground path for the low beam or high beam lamps through G201, depending on the dimmer switch positon.

Both the headlight switch and the headlamp relay can provide a ground for the headlamps for manual or automatic headlight operation. The headlights may be switched to high beam by pulling the dimmer switch handle toward the driver until the high beam dimmer switch is activated. When the dimmer switch is placed in the HIGH BEAM position, the indicator lamp and the high beam lamps are grounded and illuminate.

The flass to pass feature can be operated with the low beams OFF or ON. The high beams may be momentarily turned on or flashed with the dimmer switch handle. When the headlamp dimmer switch handle is pulled toward the driver, the flash-to-pass switch closes grounding the high beam circuit at G201, both high beams will remain on until the driver releases the switch handle. If the low beam headlamps were on during a flash-to-pass operation, they will remain on.

The Daytime Running Lamps (DRL) are designed to automatically operate exterior lights depending on outside light conditions. The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level. When the BCM receives this signal it will then operate the DRL in either day mode or low light mode depending on the light level.

The BCM has a delayed headlamp control feature that will leave the headlamps ON for a 90 seconds after the ignition switch is turned OFF, when the ambient light sensor indicates low light conditions.

The BCM will not operate any headlamps or exterior lamps, if the park brake is applied before the ignition switch is turned to the RUN position. This allows the driver to start the vehicle and keep the headlamps OFF, as long as the park brake is applied. The BCM will activate the headlamps when the park brake is released with the ignition switch in the RUN position. This feature functions only when the park brake is applied before the ignition switch is turned to the RUN position. The headlamps will turn OFF, if the park brake is applied after the ignition switch is turned to the RUN position.