Voltage is applied from the PK LPS fuse #9 at all times through CKT 240 (ORN) to the Headlamp and Panel Dimmer Switch and the Headlamp Control Module. Within the Headlamp and Panel Dimmer Switch is a 17A circuit breaker which receives power from the LIGHTING fuse #8 through CKT 42 (RED). The circuit breaker opens upon heating due to an overcurrent condition. Once the thermal elements cool the circuit breaker will reset itself, closing the contacts. Headlamp and Panel Dimmer Switch has three positions.

The three-position headlamp switch has the following positions:

When the switch is in the HEADLAMPS position, voltage is sent through CKT 1396 (LT BLU) to the headlamp input of the headlamp control module and CKT 9 (BRN) going into the park lamp input terminal of the headlamp control module. The module will then send power out through CKT 10 (YEL) to the headlamp dimmer switch and daytime running lamp module, turning on the headlights and overriding the daytime running lamps. When the headlamp and panel dimmer switch is in the PARK LAMPS, current is present only in the park lamps circuit.

The headlamp control module receives power at all times also through CKT 2040 (ORN) from the AUX PWR AUTO HEADLAMPS fuse #22, and ground from CKT 150 (BLK) to ground G202. The headlamp control module has the ability to turn the headlights on, when the body control module (BCM) sends a command or the vehicle interface unit (VIU) sends a command through CKT 624 (BLK/WHT).

Other inputs for the headlamp control module include; ignition sense through CKT 39 (PNK) from the GAUGES fuse #4. This lets the module know that the Ignition is ON. When the module senses the ignition ON, the ambient light sensor input through CKT 1784 (YEL/BLK) is sensed. When the signal sent from the ambient light sensor reaches the predetermined setting the headlamp control module will automatically send power out through CKT 10 (YEL) to the headlamp dimmer switch and daytime running lamp module, turning on the headlights and overriding the daytime running lamps. The park brake warning switch also sends input to the module through CKT 1134 (LT BLU).

The headlamp dimmer switch is part of the multifunction switch on the steering column. By pulling the multifunction switch lever up along the axis of the steering column, the switch changes selections. Repeated switch operations alternate between the high beam selection and the low beam selection. With the selection of the low beams, voltage is available on CKT 12 (TAN) to the daytime running lamps (DRL) relay. When the headlights are on the relay is de-energized sending the voltage from the headlamp dimmer switch through the relay to CKT 359 (PPL) to the left and right low beam headlamps. With the selection of high beams, voltage is available on CKT 11 (LT GRN) to the high beam headlamps. Voltage is also sent to the instrument cluster and fog lamp relay. Because the headlamps are grounded through CKT 150 (BLK) to G113 for the left and G112 for the right, current flows through the low beam filaments. The headlamps light.