Headlights (USA)

Exterior Lights

How the Headlights Circuit Works (USA)

WARNING: A transient high tension (25,000 V) occurs at the 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 ob serve 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 MICU, combination switch control unit, and the relay control module control the headlights circuit. The high beam and low beam headlight relays are located within the relay control module.

Power Supply
Battery voltage is supplied at all times through fuse 7 (in the driver's under-dash fuse/relay box) to the MICU and to the combination switch control unit. Battery voltage is supplied with the ignition switch in ON (II) or START (III) through fuse 21 (in driver's under-dash fuse/relay box) to the MICU and to the combination switch control unit.

System Description

Daytime Running Lights (DRL)
The DRL system works by supplying a reduced voltage to the high beam headlights. The DRL control unit receives battery voltage from fuse 3 and from fuse 21 (in the driver's under-dash fuse/relay box) and distributes the voltage to the high beam headlights at approximately 2 volts. The illumination of the headlights is reduced for DRL operation.

When the parking brake is applied the DRL system will not operate. The parking brake ground signal is supplied to the gauge control module and that in formation is multiplex communicated to the relay control module.

Because of the multiplex operation of the head lights, the headlights will always reset to the low beams when the ignition key is cycled.

High and Low Beams
The high and low beam headlight relays are located within the relay control module. The relays receive battery voltage at all times. The relay control module and the multiplex system control the grounding and operation of the relays. The combination switch control unit 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 HIGH or LOW, 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.

Flash-to-Pass
The combination switch control unit receives in formation signals about operating conditions from the headlight switch and from the dimmer switch. When the dimmer switch is pulled to PASSING, 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 Feature
When the headlight switch is set to the AUTO position, the headlights and all exterior lights will turn on if the light sensor on the top of the dash senses a low ambient light condition.

The relay control module controls the headlight relays and the taillight relay to illuminate all the lights.

Automatic Lighting Off Feature
The relay control module controls the headlight relays and the taillight relay. If the headlight switch is left in PARK or HEAD, the ignition key is removed, and the vehicle is locked, the MICU will inform the relay control module to turn the exterior lights off within 15 seconds after the doors are closed. When the driver's door is unlocked or opened, the lights will turn back on.