Headlamp: Description and Operation

How the Headlights Circuit Works

The Headlights circuit is composed of the Driver's MICU, the Passenger's MICU, the Headlight Switch, the Dimmer/Flash-to-Pass Switch, the Left and Right Headlights, and the High Beam Indicator. The Driver's MICU and Passenger's MICU control the Headlights with built-in Low and High Beam Control Circuits based upon the position of the Headlight Switch and the Dimmer/Flash-to-Pass Switch. The Driver's MICU and the Passenger's MICU communicate Headlights information directly between each other and via B-CAN.

Low Beams

When the Headlight Switch is moved to the ON position with the Dimmer/Flash-to-Pass Switch in the LOW position, a ground signal is supplied to terminal R8 of the Driver's MICU. The Driver's MICU and the Passenger's MICU activate their Low Beam Control Circuits, supplying battery voltage to the Low Beam Headlights, causing them to come on.

High Beams

When the Headlight Switch is moved to the ON position with the Dimmer/Flash-to-Pass Switch in the HIGH position, ground signals are supplied to terminals R8 and R22 of the Driver's MICU. The Driver's MICU and the Passenger's MICU activate their Low and High Beam Control Circuits, supplying battery voltage to the Low and High Beam Headlights, causing them to come on.

Flash-to-Pass

When the Dimmer/Flash-to-Pass Switch is moved to the PASSING position, a ground signal is supplied to terminal R21 of the Driver's MICU. The Driver's MICU and the Passenger's MICU activate their Low and High Beam Control Circuits for as long as the switch is held, supplying battery voltage to the Low and High Beam Headlights, causing them to come on.

Daytime Running Lights (DRL)

The DRL circuit is composed of the Driver's MICU, the Passenger's MICU, the Left and Right Headlights, and the DRL Indicator. The DRL circuit operates with the Ignition Switch in ON (II), the Headlights off (Headlight Switch in OFF or in PARKING position), and the Parking Brake released.

When the DRL circuit is on, the Driver's MICU and the Passenger's MICU activate their High Beam Control Circuits on and off (duty cycle), which provides a reduced voltage (approximately 6-8 volts) to the High Beam Headlights. This reduced voltage causes the High Beam Headlights to come on with a reduced brightness. The DRL Indicator also illuminates.

NOTES:
- The DRL circuit is disabled when the Ignition Switch is turned to OFF (0). To keep the DRL circuit from coming on, apply the Parking Brake while the Ignition Switch is in OFF (0). When the Ignition Switch is turned back to ON (II), the DRL circuit will not come on until the Parking Brake is released.
- The Headlights revert back to normal operation when the Headlight Switch is moved to the ON position.

Automatic Lighting (Automatic Lighting)

When the Headlight Switch is in the AUTO position, the Driver's MICU and Passenger's MICU receive an automatic lighting signal. When the Automatic Lighting Sensor detects low ambient light, a lights-on signal is transmitted to the Driver's MICU and the Passenger's MICU. The Driver's MICU and the Passenger's MICU activate their Low Beam Control Circuits, supplying battery voltage to the Low Beam Headlights, causing them to come on.