Your 2003 Chevrolet Silverado 2500HD has two horns installed. When one fails you may notice not only a drop in sound but the tone of your horn sound will also be affected. To not only locate but service the horns, you may have to disconnect the battery, especially if servicing the left horn. Always remember that you need to remove the negative terminal of the battery first to safely disconnect it.
The left horn is located under the battery tray on the left lower corner of the radiator core support. The right horn is located on the right lower corner of the radiator core support.
