Battery voltage is applied at all times to the horn relay (Relay 15) through the 740 circuits.

When the horn switch is closed, the chassis ground (circuit 150) is applied from the steering wheel through circuit 28 grounding the coil of the relay and energizes the horn relay.

Circuit 1550 also provides a redundant ground to the steering wheel.

The horn relay can also be energized by the BCM grounding circuit 28.

When the horn relay is energized, the switch in the horn relay closes and applies battery voltage to the horns through circuit 29. Circuit 29 activates the horns. The horns are grounded through circuit 1350 to G101.