Circuit Operation
WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch grounds the horn relay control circuit. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horn through the horn control circuit. The horn sounds as long as ground is applied to the horn relay control circuit.