Exterior Lighting Systems Description and Operation: Headlamps

The headlamps may be turned ON 2 different ways. First, when the driver places the headlamp switch in the HEAD position, for normal operation. Second, with the headlamp switch placed in the AUTO position, during operation in low light conditions.

On vehicles with manual headlamps, the LH HDLP and RH HDLP fuse in the fuse block - underhood, supply battery positive voltage to both low beam lamps and high beam lamps at all times. The low beam and high beam circuits continue through the fuse block - underhood, through the body control module (BCM), and to the headlamp switch. The low beam or high beam circuit then, depending on the position of the dimmer switch, continues through 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 G203. The low beam and high beam circuits are monitored by the BCM.

On vehicles with automatic headlamps, the LH HDLP and RH HDLP fuse in the fuse block - underhood, supply battery positive voltage to both low beam lamps and high beam lamps at all times. The low beam and high beam circuits continue through the fuse block - underhood, through the BCM, and to the headlamp switch. The low beam or high beam circuit then, depending on the position of the dimmer switch, continues through the headlamp switch. The low beam and high beam circuits are monitored by the BCM. During automatic headlamp operation in low light conditions, the BCM will apply voltage to the coil side of the headlamp relay, energizing it. When the headlamp relay energizes, it provides a ground path for the low beam or high beam lamps through G203, depending on the dimmer switch position.