I've got a 3.0CL with the stock alarm. A few weeks back the chirp noise started sounding distorted before completely stopping altogether when I lock and unlock my doors. The doors still lock and the lights still flash but no Chirp. could a replacement horn do the trick or is it something much more problematic?

 

Check your wires and most notably the grounds. They often get corroded and eventually break. Run a jumper ground wire to the frame and see if the chirp comes back. If it does you need to run a new ground wire.