The headlights are controlled by the body control module (BCM) via the headlamp power relay when the headlamp switch is in the OFF/AUTO position. When in the OFF/AUTO mode, the BCM receives a signal (voltage) from the ambient light sensor and based on the voltage from the sensor the BCM turns the headlights ON. The headlights can also be turned on by placing the multifunction switch (headlamp switch) in the ON (HEAD) position.

The headlamp power relay is fed by the BCM and the battery B+ buss bar in the underhood fuse block. The BCM supplies current to the relay based on the input from the ambient light sensor via CKT 352 (WHT).

The headlamp power relay output feeds the LH HDLP and RH HDLP fuses to supply current to the low and high beam lamps on CKT 712 and CKT 198. The ground for both the low and high beam lamps is supplied via CKT 524 (PPL) and CKT 525 (YEL) to the flash to pass relay. The flash to pass relay uses CKT 850 (BLK) for a ground to G117.

Some circuits are monitored by the BCM, and upon failure may set a DTC.