Circuit Description
How the Circuit WorksWARNING: 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 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.
- To prevent electrocution, do not service the headlight assembly in wet conditions, such as rain or snow, near a sprinkler system, or when your hands are wet.
- 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, control block (in the under-hood fuse/relay box), and the multiplex integrated control system control the headlights circuit. The high beam and low beam headlight relays are solid-state relays within the under-hood fuse/relay box.
Power Supply
Fuse 7 (in the under-dash fuse/relay box) supplies battery voltage at all times to the MICU, the control block in the under-hood fuse/relay box, and the combination switch control unit. Fuse 21 (in the under-dash fuse/relay box) supplies battery voltage with the ignition switch in ON (II) or START (III) to the MICU, the control block in the under-hood fuse/relay box, and the combination switch control unit.
System Description
Daytime Running Lights (DRL)
The DRL system works by supplying battery voltage to dedicated lights. The control block (in the under-hood fuse/relay box) controls the DRL system. Fuses 1 and 2 in the under-hood fuse/relay box supply battery voltage to the left and right DRL bulbs.
Starting the engine with the parking brake applied prevents the DRL bulbs from lighting. Releasing the parking brake causes the control block in the under-hood fuse/relay box to supply voltage to the DRL bulbs. Applying the parking brake while the engine is running does not extinguish the DRL bulbs. Pressing the parking brake supplies a ground signal to the gauge control module sending a signal to the control block of the under-hood fuse/relay box via the B-CAN network.
The multiplex information communication system resets headlights to the low beams when the ignition key is cycled.
High and Low Beams
Fuse 6 (in the under-hood fuse/relay box) supplies battery voltage at all times to the low beam headlight relay. Multi-fuse 3 (in the main under-hood fuse box) supplies battery voltage at all times to the high beam headlight relay and the control block in the under-hood fuse/relay box.
Turning on the headlight switch and setting the dimmer switch to HIGH or LOW supplies information from both switches to the combination switch control unit. The combination switch control unit transmits the information across the multiplex communication lines. The control block in the under-hood fuse/relay box grounds the appropriate high or low beam relay to operate the requested headlights.
The back-up headlight signal circuit from the headlight switch to the control block within the under-hood fuse/relay box and the MICU in the under-dash fuse/relay box allows the low beam headlights and parking lights to operate in case of multiplex information system failure. In this event, neither high beam headlights nor fog lights will operate.
Flash-to-Pass
Pulling the dimmer switch to PASSING causes the combination switch control unit to transmit the information across the multiplex communication lines to the control block in the under-hood fuse/relay box and the MICU in the under-dash fuse/relay box. The control block in the under-hood fuse/relay box grounds the high beam relay operating the high beam headlights.
Automatic Lighting Feature
Setting the headlight switch the AUTO position controls the headlights and parking lights based on the signal received from the sunlight sensor on the top of the dash. In low ambient light conditions, the control block in the under-hood fuse/relay box turns on the lights. In high ambient light conditions, the control block in the under-hood fuse/relay box turns off the lights.
Automatic Lighting Off Feature
The control block in the under-hood fuse/relay box controls the headlights relay and the park lights relay. Removing the ignition key from the ignition switch with the headlight switch in PARK or HEAD signals the control block to turn off the exterior lights 15 seconds after the doors are closed. Unlocking or opening the driver's door turns the lights back on.