Headlamp: Description and Operation

How the Headlights Circuit Works

The MICU and the combination light switch control the headlights circuit. The high beam transistors and low beam headlight relay are located within the MICU.

Power Supply
Battery voltage is supplied at all times through fuses 18 and 21 (in the under-dash fuse/relay box) to the high beam transistors and low beam relay located within the MICU.

System Description

Low Beams
When the headlight switch is moved to the ON position, the combination light switch provides a signal to the MICU to energize the low beam relay (located inside the MICU). Once the relay is energized, voltage is supplied to the low beam headlights.

High Beams
When the headlight switch is moved to the ON position, and the dimmer/flash-to-pass switch is moved to the HIGH position, the combination light switch provides a signal to the MICU to energize the high beam transistors and low beam relay (located inside the MICU). Once they are energized, voltage is supplied to the high and low beam headlights.

Flash-to-Pass
When the dimmer/flash-to-pass switch is moved to the PASSING position, the combination light switch provides a signal to the MICU to energize the high beam transistors and low beam relay (located inside the MICU). Once they are energized, voltage is supplied to the high and low beam headlights.

DRL
The MICU controls DRL operation. The following conditions must be met for the headlights to operate in DRL mode:
- The ignition switch is in the ON (II) position
- The headlight switch is in the OFF position
- The parking brake is released

When all three conditions are met, the MICU will supply a reduced voltage to the high beam headlights.