This is the procedure for enabling/disabling the horn chirp when you press the lock button on the Remote Keyless Entry transmitter.
1. Enter vehicle, close all doors, and fasten seatbelt (to avoid unwanted chimes)
2. Place key in ignition and turn to ON (do not start)
3. Press and hold UNLOCK button on the transmitter for five seconds
4. While still holding UNLOCK, press the LOCK button on the transmitter for one second then release both buttons.
5. You will hear a single chime indicating programming is complete.
This is a toggling option. To change it back, simply repeat the process.