Battery voltage is applied at all times to the horn relay coil feed circuit. When the horn switch is closed, ground from the steering wheel travels through the horn relay control circuit and energizes the horn relay. Note: There is also a redundant ground to the steering wheel. The horn relay can also be energized by the BCM. The BCM can also ground the horn relay control circuit. When the horn relay is energized, the switch in the horn relay closes. This action applies battery voltage to the horns through the horn feed circuit, causing the horns to sound. The horns are always connected to ground.