The horn relay supplies battery positive voltage (B+) to the horns when energized. Battery positive voltage (B+) is supplied at all times to the coil side feed circuit and the switched input circuit of the horn relay. Pressing the horn switch grounds the horn relay control circuit. The horn relay control circuit is also grounded by the dash integration module (DIM) horn ON output. The DIM receives its command to turn on the horns via a class 2 message. The horns sound until the horn switch is released or the DIM releases the horn ON output.