Circuit/System Description

The low beam headlamps are controlled by the BCM through the headlamp low beam relay, and the high beams are controlled by the BCM through the high beam relay. Both relays are supplied battery voltage and are energized when the BCM grounds the low side drive control circuits. The headlamp on switch and high/low beam select switch signal circuits are referenced from battery voltage by the BCM. When a switch is activated the signal circuit is grounded, and the BCM determines the switch is active when the signal circuit voltage is low.