Headlights (USA)
How the Headlights-USA Circuit WorksWARNING: A transient high tension (25,000 V) occurs at bulb sockets of the high intensity discharge (HID) lamps when the combination light switch is turned ON. It may cause serious electrical shock or electrocution if you do not observe the cautions below.
CAUTION:
- Never turn on the combination light switch before fitting the HID bulbs to their bulb sockets and completing the reassembly of the headlight assembly.
- Do not service the headlight assembly in wet conditions, such as rain or snow, near a sprinkler system, or when your hands are wet to prevent electrocution.
- Do not touch the surface of the HID bulbs with your bare hands and do not stain it with any oils or fats.
- Do not disassemble the inverter unit and the igniter unit.
- Do not turn on the HID bulb by using a power source other than the battery mounting on the vehicle.
The headlight circuit is controlled by the MICU. The high beam and low beam headlight relays are located within the relay control module. Refer to the multiplex section of this ETM for more multiplex information.
Power Supply
With the ignition switch in the ON (II) or START (III) position, battery voltage is applied through fuse 21 to the MICU and to the combination switch control unit.
Fuse 7 is hot at all times and supplies battery voltage to the MICU and to the combination switch control unit.
System Description
High and Low Beams
The high and low beam headlight relays are located within the relay control module (under-hood fuse/relay box). The relays receive battery voltage at all times. The grounding and operation of the relays are controlled by the multiplex system.
The combination switch control unit in the steering column receives information signals about operating conditions from the headlight switch and from the dimmer switch.
When the headlight switch is turned on and the dimmer switch is set to the HIGH or LOW position, the information from both switches is processed by the combination switch control unit and transmitted from control unit to control unit across the multiplex communication lines. The relay control module will then ground the appropriate high or low beam relay to operate the necessary headlights.
Because of the multiplex operation of the headlights, the headlights will always reset the low beams when the ignition key is cycled.
Flash-to-Pass
The combination switch control unit in the steering column receives information signals about operating conditions from the headlight switch and from the dimmer switch.
When the dimmer switch is pulled back and moved to the PASSING position, the information from the dimmer switch is processed by the combination switch control unit and transmitted from control unit to control unit across the multiplex communication lines. The relay control module will then ground the high beam relay to operate the passing lights.
Automatic Lighting Off Feature
On vehicles equipped with the automatic lighting off feature, the relay control module controls the headlight relays and the taillight relay. If the headlight switch is left in the PARK or HEAD position, the ignition key is removed, and the vehicle is exited, the relay control module will automatically turn the exterior lights off within 15 seconds after the doors are closed. When the driver's door is unlocked or opened, the control unit automatically turns the lights back on.