Circuit Description
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The headlamp washer switch signal circuit is supplied a 12-volt reference through a resistor then monitored within the body control module (BCM). The headlamp washer switch is open when in an inactive state. When the headlamp washer switch is activated the signal circuit is closed to ground. When the headlamp washer switch signal circuit is closed to ground the reference voltage is dropped across the resistor within the BCM. The low voltage on the headlamp washer switch signal circuit indicates to the BCM the switch status is active.